# Development and Evaluation of Colorado's Low Emitter Index

Colorado Department of Public Health and Environment May 2007 Prepared by: Mobile Sources Air Pollution Control Division Colorado Department of Public Health and Environment and Peter M McClintock, PH.D . Applied Analysis 891 Tiburon Blvd . Peter.mcclintock@comcast.net•Page 2Introduction Colorado's inspection and maintenance (l/M) program includes a Clean Screen element that allows vehicle owners the option of being exempted from their required l/M240 inspection, if their vehicle is determined clean . Currently, to qualify as clean a vehicle must be seen by a Remote Sensing Device (RSD) a minimum of two times within 12 months prior to its required l/M240 inspection, with emissions measurement less than 200ppm and .5% for HC and CO respectively. The Colorado Department of Public Health and Environment (CDPHE) is proposing to add a hybrid method of identifying clean vehicles that combines a single clean RSD measurement with a Low Emitter Index (LEI) criterion . The LEI qualifies vehicles as Clean Screen candidates based on a historically low probability of emissions failure for similar vehicles. The addition of the LEI hybrid method will increase the productivity of the existing Clean Screen program and allow more vehicle owners to take advantage of the convenience of clean screening without jeopardizing the benefit to the current l/M program . The LEI qualification criteria will be evaluated/updated on an annual basis to ensure it is equal to or better than the current 2-hit clean screen program . Colorado's l/M program is included in both the One Hour Ozone Maintenance Plan and Eight Hour Ozone Early Action Compact (EAC) , as a mobile source control strategy. The program as modeled prohibits Colorado from evaluating more than 50% of the l/M eligible fleet. The inclusion of the proposed LEI hybrid method will not exceed this threshold . This document describes how the LEI was developed along with the comparison of the projected performance ofthe hybrid method to the current 2-hit Clean Screen method . Source Data and Vehicle Grouping An LEI lookup table hasb een developed using 2005 and 2006 initial IM240 inspection results. Colorado tests AWD and traction control vehicles on 4WD dynes so there are few models that do not receive IM240. Vehicles are grouped using : Colorado1 Vehicle Type : LDGV, LDGT1 , LDGT2, HDGT1 , HDGT2 Model Year: the tenth character from the VIN Make : decoded from the VIN; Model : decoded from the VIN; Engine Displacement: decoded from the VIN; Only groups containing 20 or more vehicles will be retained in the combined profile in order to avoid concerns over statistical variability in small sample sizes. Missouri had used the first five characters of the VIN in lieu of Make and Model. Colorado proposes using Make and Model as decoded from the VIN using the Polk program, since this approach appears to better and more consistently differentiate Make/Model than the Missouri approach .

1 In the Colorado data, light trucks are defined using four types : LDGT1, LDGT2 , HDGT1, and HDGT2 . The first pair roughly corresponds to the EPA's LDGT1 and the second pair corresponds to EPA's LDGT2 . •Page 3Table 1 compares the use of alternative sets of LEI vehicle groupings. It shows the number of source vehicles, the number of bins with 20 or more results, and the percentage of all source veh icles in these classifications . Coverage of source veh icles is highest with the proposed scheme . Table 1 LEI Vehicle Vehicles >=20 HC/CO NOx HC/CO + Fleet Groupings Bins Fail% Fail% NOxFail % Coverage % None (All vehicles) 1 ,557 ,509 N/A 2.67% 0. 16% 2.83% 100% Veh . Type , Model Year , First 5 VIN Char., Polk Engine 1,439 ,382 8,438 2 .54% 0.16% 2 .7% 92.4% Displacement,# of Cvlinders Veh . Type, Model Year , First 5 VIN Char. , Polk Engine 1,450,518 8 ,388 2 .53% 0. 16% 2.69% 93 . 1% Displacement Veh. Type, Model Year, Polk Make, Polk Model, Polk Engine 1,476,842 6,817 2.58% 0.16% 2.74% 94.8% Disolacement The LEI table generated using 2005/2006 l/M test results will typically be applied to vehicles inspected in 2007 and part of 2008 . Colorado has a four-year exemption for new veh icles . Although some inspections on these models are performed , the 2005/2006 inspection results may leave gaps in the profile for models that will be four-year old vehicles in 2007/2008 , e .g . 2003 and 2004 models . The gaps will be filled to a large extent by assuming newer year vehicles, will perform similarly (or better) than the same model of an earlier year, for which performance statistics are available, e .g . 2003 and newer Acura MDXs will perform at least as well as 2002 Acura MDXs. LEI Emissions Perfonnance The values listed below were computed for each vehicle group. The average excess emissions per veh icle are the sum of the vehicle emissions exceeding the Colorado standards divided by the number of vehicles in the group. These g/mi values are usually small compared to g/mi standards because most vehicles do not add any excess emissions and all vehicles are included in the denominator. Initial tests HC/CO fails HC/COfail % NOxfails NOxFail% Overall fail% Average Excess HC g/mi per vehicle Average Excess CO g/mi per vehicle Average Excess NOx g/mi per vehicle The LEI clean screening effectiveness will be targeted towards the most critical pollutants by adjusting the selection criteria. · Figure 1A plots the cumulative percentage of excess emissions vs . the percentage of vehicles when LEI groups are ranked by tailpipe emissions fail rate . Figure 1B is the same chart with an expanded yaxis. These charts indicate when groups of vehicles are ranked by increasing tailpipe fail rate , groups containing 70% of the vehicles produce only 10% of the excess HC and CO and 30% of the excess NOx. Note that total excess NOx is small compared to excess HC and CO due to Colorado's lenient NOx standards.

• Page4Figure 1A LEI Excess Emissions vs.% ofVehicles When Ranked by Tailpipe Fail Rate

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•Page 5Figures 2A and 28 show the cumulative percentage of excess emissions vs. the percentage of vehicles when LEI groups are ranked by the fail rate for HC or CO . Seventy percent ofthe vehicles produce 8% ofthe excess HC and CO . Figure 2A LEI Excess Emissions vs. % of Vehicles When Ranked by HC/CO Fail Rate 

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• Page6Figures 3A and 38 show the cumulative percentage of excess em issions vs. the percentage ofvehicles when LEI groups are ranked by excess HC. Seventy percent of the vehicles produce 5% ofthe excess HC.

•Page 7Figure 3A LEI Excess Emissions vs. % ofVehicles When Ranked by Excess HC 

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# - 0 0 10 20 30 40 50 60 70 80 90 % of VehiclesLEI Clean Screen Selection Criteria To maintain flexibility in the selection of LEI vehicles (both quantity and quality) , it is suggested that the following five criteria be considered. Colorado is proposing using only the HC/CO Fail Rate criteria however the remaining four will continue to be calculated and if necessary included as part of future LEI tables. Overall tailpipe fail rate is less than : HC/CO Fail Rate is less than Excess HC is less than : Excess CO is less than : Excess NOx is less than Xo/o Yo/o Ag/mi Bg/mi Cg/mi To ignore one or more of the criteria , either a high or a low value is entered. For example , to select all vehicle classes with an overall fail rate of less than 1%, entries would be 1 %, 99%, 99 , 99 and 99. Average excess emissions per vehicle relate more directly to mass emissions benefits than fail rate . Given two groups of vehicles with the same fail rate , one group containing poor fuel economy vehicles and one group containing good fuel economy vehicles, the group with the poor fuel economy vehicles will contribute greater excess emissions. However, using fail rate as the criteria is easier for the media and the public to understand . Hybrid Method Evaluation The hybrid method of selecting vehicles for clean screen was evaluated using 2006 data. l/M results of vehicles that would have been selected using the hybrid method are compared to the results ofthe 5% audit sample of vehicles passing the current 2-hit screen and vehicles that were identified as clean (2- hits) but for unknown reasons did not participate in the current clean screen program . Table 2 below shows that projected results for vehicles selected using the hybrid method compare favorably to the current RSD 2-hit method . Both the tailpipe and overall fail ·rates, which includes evaporative test failures, are 0.3% lower. The hybrid method was modeled using RSD CO and HC cutpoints of 0.5% and 200ppm respectively and a simple LEI HC/CO fail rate of 2%. Table 2 Clean Screen Method Evaluation Summary Number IM240 Method Sample of Tailpipe Overall l/M Fail Fail Rate Vehicles Rate Hybrid Sample 31,644 0.34% 2.6% 2006 RSD 2-hit 5% Audit Sample 1,509 0.46% 2.5% Other RSD 2-hit Sample Meeting 15,299 0.66% 2.9% Screen Criteria Combined RSD 2-hit Samples 16,808 0.64% 2.9%

•Page 8The results show that the effectiveness of the hybrid method is equivalent to that of the current clean screening method using two RSD measurements. Further investigation is being conducted to determine if the evaporative failures can be cost effectively reduced for both methods by applying an additional restriction on clean screens for models with a pattern of evaporative test failures. The remainder of this section provides details ofthe hybrid evaluation . Hybrid Evaluation Process As noted above ,the hybrid method of selecting vehicles for clean screen was evaluated using 2006 l/M results of vehicles that would have been selected using this method. Vehicle owners are notified of their clean screen eligibility one to two months prior to their registration renewal date. Change of ownership vehicles that are inspected off-cycle are ,therefore, not able to take advantage of clean screening . Historically, vehicles changing ownership have higher emissions and failure rates than other vehicles. To accurately project hybrid clean screen program performance these off-cycle tests are removed from the evaluation sample. To accomplish this, vehicles tested in 2006 were selected where their first test occurred within 23-25 months of their first test in 2004. This identified 303 ,525 vehicles tested with IM240. RSD measurements from the 12-month window in advance of the IM240 test were identified for the 303,525 vehicles. Of these, 23,521 vehicles had at least two measurements and 48,438 vehicles had a single measurement. Vehicles with two measurements would typically be considered for current 2-hit screening method . Vehicles that accepted the clean screen option would not typically have an IM240 test in 2006 and, therefore , are not typically included in the extracted sample of vehicles with two measurements described above . The extracted sample of vehicles with two measurements does include the 5% audit sample , vehicles that did not pass the screen , vehicles that did not accept the clean screen option and vehicles for which the second qualifying RSD may not have been in time to be included before the processing deadline. Veh icles with a single measurement passed the hybrid method if their HC and CO emissions were below 200ppm and 0.5% respectively on their RSD measurement and their LEI group had an HC/CO fail rate of less than 2%. Results are compared to both the 5% audit sample and the other RSD 2-hit vehicles screened using the current 2-hit method . Since vehicles with two qualifying measurements would not be eligible for the hybrid method they were not considered part of the hybrid evaluation . However, vehicles from this group that would have met the 2-hit RSD screen criteria provide another point of reference for comparison with the effectiveness of the hybrid method . Therefore, results for three samples are considered in the following charts and tables : • 2006 RSD 2-hit Audit sample • Hybrid Method sample • Other RSD 2-hit sample ; vehicles with two RSD measurements that met the 2-hit screen criteria . Figure 4 shows that MY distributions ofvehicles meeting the screening criteria from the 'Hybrid Sample' and the 'Other 2-Hit Sample' vehicles are similar to the 'Audit Sample' except that the 'Audit Sample' includes more 2002 models. Most 2002 models were not tested in 2004 and , as a result of the sample •Page 9selection method described above, were not included in the 'Hybrid Sample' or the 'Other 2-hit Sample'. Since the 2002 models are the newest full model year, and are expected to be virtually all clean, their omission does not compromise the hybrid evaluation although the evaluated hybrid effectiveness may appear to be less good than if all these 2002 models had been included . Figure 4 - Vehicle Age Distribution of Clean Screen Vehicles Age Distribution ofVehicle Samples Meeting Clean Screen Criteria

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.....Tables 3, 4 , 5 and 6 show the IM240 test results for the 'Aud it Sample', 'Hybrid Sample', 'Other RSD 2-hit Sample', and 'Aud it Sample and Other RSD 2-HitS ample Combined' . The tables show the MY distribution , the tailpipe fail rate , the overall fail rate and the average IM240 g/mi emissions of vehicles passing the screens. Despite the absence of a full complement of 2002 models, the average em issions of vehicles passing the Hybrid method are lower than the 'Audit Sample' by 0.01 , 0. 1 and 0.01 g/mi for HC , CO and NOx respectively. The average emissions of vehicles passing the Hybrid method are lower than the 'Other RSD 2-hit Sample' by 0.05 , 0.7 and 0.09 g/mi for HC , CO and NOx respectively. The Hybrid method is therefore at least as effective as the RSD 2-hit method . Table 3 -Audit Sample 2006 Audit Sample Vehicles Passing 2-Hit Screen with RSD CO <0.5% and HC <200ppm Model Fraction IM240 IM Model Vehicles IM240 Overall IM240 IM240 IM240 Year of Tailpipe Overall Year Tailpipe Failures Avg . Avg . Avg . Screen Fail Fail Failures HC 

## co NOx Passes Rate Rate g/mi g/mi g/mi 1982 0% 0.00% 0.0% 1982 0 0 0 

### - - - 1983 0% 0.00% 0.0% 1983 0 0 0 

## - - - 1984 0% 0.00% 0.0% 1984 1 0 0 4 .37 21 .2 4.20 1985 0% 0.00% 0.0% 1985 1 0 0 0.98 12 .9 2.02 1986 0% 0.00% 0.0% 1986 2 0 0 1.92 14.7 2 .87 1987 0% 0.00% 0.0% 1987 2 0 0 1 .12 8. 1 1 .72 1988 1% 7.69% 7.7% 1988 13 1 1 1.45 10.7 1 .82 1989 1% 0.00% 9 .1% 1989 11 0 1 0.93 7.8 2. 19 1990 1% 4 .76% 9 .5% 1990 21 1 2 1 .04 12.2 2 .00 1991 1% 0.00% 0.0% 1991 15 0 0 0.78 8.8 1 .69 1992 2% 0.00% 0.0% 1992 23 0 0 1 .04 9.7 2 .07 1 993 2% 0.00% 2 .9% 1993 34 0 1 0.74 7.3 1.47 1994 3% 0.00% 0.0% 1994 50 0 0 0.56 5.8 1 .35 1995 4% 1 .54% 7.7% 1995 65 1 5 0.62 5.5 1 .30 1 996 6% 0.00% 2.1% 1996 96 0 2 0.38 4 .3 1 .28 1997 6% 0.00% 1 .0% 1997 98 0 1 0.37 4 . 1 1 .30 1998 12% 0.56% 2 .2% 1998 178 1 4 0.29 3.6 1 .03 1999 8% 0.84% 2.5% 1999 119 1 3 0.30 3.0 1 .02 2000 17% 0.78% 1 .9% 2000 258 2 5 0.20 2 .8 0.68 2001 10% 0.00% 2 .6% 2001 153 0 4 0.12 2.2 0.48 2002 22% 0.00% 2.4% 2002 338 0 8 0.11 1 .8 0.47 2003 2% 0.00% 0.0% 2003 31 0 0 0. 14 2.6 0.60 2004 0% 0.00% 0.0% 2004 0 0 0 

## - - - 2005 0% 0.00% 0.0% 2005 0 0 0 

### - - - Total 100% 0.46% 2.5% 1,509 7 37 0.31 3.6 0.90 I •Page 11Table 4 - Hybrid Sample Projected 2006 Hybrid Screen Passes: RSD CO <0.5% & HC < 200ppm, LEI HC/CO Failure < 2% Model Fraction IM240 IM Model Vehicles IM240 Overall IM240 IM240 IM240 Year of Tailpipe Overa' ll Year Tailpipe Failures Avg . Avg . Avg . Screen Fail Fail Failures HC 

## co NOx Passes Rate Rate g/mi g/mi g/mi 1982 0% 0.00% 0.0% 1982 1 0 0 4 .00 31 .8 3. 10 1983 0% 0.00% 0.0% 1983 0 - 0 0 

### - - - 1984 0% 6 .25% 18.8% 1984 16 1 3 1 .76 20.7 2.14 1985 0% 0.00% 16.7% 1985 6 0 1 1.43 14.8 1 .93 1986 0% 0.00% 0.0% 1986 38 0 0 0.99 11 . 1 1 .92 1987 0% 0.00% 18.2% 1987 11 0 2 0.99 10.2 2.17 1988 0% 0.00% 3.3% 1988 30 0 1 0.95 9.4 1 .53 1989 0% 0.00% 3.1% 1989 32 0 1 0.79 8.4 1 .68 1990 1% 0.56% 3.3% 1990 180 1 6 0.82 7.8 1 .76 1991 1% 0.00% 4 .2% 1991 236 0 10 0.76 7.7 1 .74 1992 2% 0.16% 2 .3% 1992 607 1 14 0.67 7. 1 1 .53 1993 2% 1 . 15% 4.3% 1993 697 8 30 0.70 7.3 1.71 1994 3% 0.91% 3.4% 1994 993 9 34 0.56 5.9 1.34 1995 5% 0.84% 3. 1% 1995 1,426 12 44 0.51 5. 1 1.34 1996 9% 0.46% 3.5% 1996 2,820 13 98 0.38 4 .2 1.13 1997 9% 0.51% 3.8% 1997 2 ,943 15 113 0.36 4. 1 1 .11 1998 16% 0.29% 2 .0% 1998 5,214 15 103 0.30 3.4 0.91 1999 12% 0.21% 2 .3% 1999 3,781 8 87 0.27 3.0 0.86 2000 24% 0.23% 2 .3% 2000 7,538 17 170 0.20 2 .5 0.66 2001 8% 0.17% 2.2% 2001 2 ,387 4 52 0. 14 2.1 0.48 2002 5% 0.25% 2 .3% 2002 1,601 4 37 0.12 2.0 0.44 2003 2% 0.00% 1.2% 2003 753 0 · 9 0.09 1 .7 0.36 2004 1% 0.00% 1.2% 2004 326 0 4 0.08 1 .5 0.29 2005 0% 0.00% 0.0% 2005 8 0 0 0.07 1 .3 0.28 Total 100% 0.34% 2.6% 31,644 108 819 0.30 3.5 0.89

•Page 12Table 5 - Other RSD 2-Hit Sample Other Vehicles Passing 2-hit Screen with CO <0.5% and HC <200ppm Model Fraction IM240 IM Model Vehides IM240 Overall IM240 IM240 IM240 Year of Tailpipe Overall Year Tailpipe Failures Avg . Avg . Avg . Screen Fail Fail Failures HC 

## co NOx Passes Rate Rate g/mi g/mi g/mi 1982 0% 0.00% 0.0% 1982 4 0 0 1.96 15.6 3.15 1983 0% 0.00% 0.0% 1983 2 0 0 1 .58 11.5 4.15 1984 0% 0.00% 7 . 1% 1984 14 0 1 1 .88 21 .2 2.46 1985 0% 4 .35% 4 .3% 1985 23 1 1 1 . 15 14. 1 2.33 1986 0% 2 .22% 4.4% 1986 45 1 2 1 .30 13.9 2.28 1987 0% 5.45% 9 .1% 1987 55 3 5 1 . 13 11 .9 2.33 1988 1% 1 .71% 4 .3% 1988 117 2 5 1 .13 11.9 1 .95 1989 1% 2 .70% 5.4% 1989 111 3 6 1 .04 11.6 1 .94 1990 2% 0.87% 6 . 1% 1990 230 2 14 0 .89 8.7 1 .79 1991 2% 1 .96% 7.5% 1991 255 5 19 0 .84 8.8 1 .83 1992 3% 3.42% 7 .8% 1992 409 14 32 0 .82 9.4 1 .72 1993 3% 1 .61% 4.6% 1993 436 7 20 0.73 7 .9 1 .86 1994 4% 1 .53% 4. 1% 1994 589 9 24 0.70 7.4 1 .59 1995 5% 2 .08% 5 .6% 1995 818 17 46 0.63 6 .2 1.45 1996 8% 0 .51% 2 .1% 1996 1 , 167 6 25 0.41 4 .7 1 .26 1997 8% 0 .89% 3.7% 1997 1 ,237 11 46 0.40 4.4 1 . 17 1998 1 3% 0.63% 2 .3% 1998 2 ,054 13 48 0.31 3.9 0.97 1999 10% 0.06% 2 .0% 1999 1 ,578 1 32 0 .27 3.2 0.88 2000 20% 0.20% 2 .2% 2000 3 ,037 6 67 0 .20 2.7 0.66 2001 7% 0.00% 2 .3% 2001 1 ,142 0 26 0 .13 2.2 0.50 2002 5% 0.00% 1.6% 2002 770 0 12 0 .11 1 .8 0.43 2003 5% 0.00% 1 .3% 2003 775 0 10 0 .09 1 .6 0 .36 2004 3% 0.00% 0.5% 2004 420 0 2 0 .08 1 .5 0.29 2005 0% 0.00% 0.0% 2005 11 0 0 0.07 1.6 0.19 Total 100% 0.66% 2.9% 15,299 101 443 0.35 4.2 0.98

•Page 13Table 6 - Audit Sample and Other RSD 2-Hit Sample Combined 2006 Audit Sample+ Other 2-Hit Passing 2-Hit Screen with RSD CO <0.5% and HC <220ppm Model Fraction IM240 IM Model Vehicles IM240 Overall IM240 IM240 IM240 Year of Tailpipe Overall Year Tailpipe Failures Avg . Avg . Avg . Screen Fail Fail Failures HC 

## co NOx Passes Rate Rate g/mi g/mi g/mi 1982 0% 1982 4 

### - - 1 .96 15.61 3. 15 1983 0% 1983 2 

### - - 1 .58 11 .53 4 .15 1984 0% 0.00% 6.7% 1984 15 

## - 1 2 .05 21 .23 2 .58 1985 0% 4.17% 4 .2% 1985 24 1 1 1 . 15 14.04 2 .31 1986 0% 2 . 13% 4 .3% 1986 47 1 2 1 .33 13.96 2.30 1987 0% 5.26% 8.8% 1987 57 3 5 1 .13 11 .77 2 .31 1988 1% 2 .31% 4 .6% 1988 130 3 6 1 .17 11 .80 1 .94 1989 1% 2.46% 5.7% 1989 122 3 7 1.03 11 .27 1 .96 1990 1% 1.20% 6.4% 1990 251 . 3 16 0.91 9.00 1 .81 1991 1% 1.85% 7.0% 1991 270 5 19 0.84 8.83 1 .82 1992 3% 3.24% 7.4% 1992 432 14 32 0.84 9.43 1 .74 1993 3% 1.49% 4 .5% 1993 470 7 21 0.73 7.89 1 .83 1994 4% 1.41% 3.8% 1994 639 9 24 0.69 7.28 1 .57 1995 5% 2 .04% 5.8% 1995 883 18 51 0.63 6. 19 1.44 1996 8% 0.48% 2 . 1% 1996 1 ,263 6 27 0.41 4 .71 1 .27 1997 8% 0.82% 3.5% 1997 1 ,335 11 47 0.39 4.40 1 . 18 1998 13% 0.63% 2 .3% 1998 2 ,232 14 52 0.31 3.86 0.97 1999 10% 0.12% 2 .1% 1999 1 ,697 2 35 0.27 3.16 0.89 2000 20% 0.24% 2.2% 2000 3,295 8 72 0.20 2 .69 0.67 2001 8% 0.00% 2 .3% 2001 1 ,295 

### - 30 0. 13 2.15 0.50 2002 7% 0.00% 1 .8% 2002 1 , 108 

### - 20 0. 11 1.82 0.44 2003 5% 0.00% 1.2% 2003 806 

### - 10 0.09 1.67 0.37 2004 2% 2004 420 

### - 2 0.08 1 .51 0.29 2005 0% 2005 11 

### - - 0.07 1 .58 0.19 Total 100% 0.64% 2.9% 16,808 108 480 0.35 4.1 0.97

•Page 14United States Environmental Protection Agency Air and Radiation 

# &EPA Performing Onboard Diagnostic System Checks as Part of a Vehicle Inspection and Maintenance Program EPA420-R-01-015 June 2001



### @ Printed on Recycled Paper

### EPA420-R-01-015 June 2001



# Performing Onboard Diagnostic System Checks as Part of a Vehicle Inspection and Maintenance Program

David Sosnowski Edward Gardetto Transportation and Regional Programs Division Office ofTransportation and Air Quality U.S. Environmental Protection Agency

NOTICE This technical report does not necessarily represent final EPA decisions orpositions. It is intended to present technical analysis of issues using data that are currently available. Thepurpose in the release of such reports**i~** 

### tofacilitate the exchange of technical information and to inform thepublic of technical developments which may form the basis for a final EPA decision, position, or regulatory action.

### Performing Onboard Diagnostic System Checks as Part of a Vehicle Inspection and Maintenance Program June 2001 Introduction The Clean Air Act as amended in 1990 (CAA) requires the Environmental Protection Agency (EPA) to set guidelines for states to follow in designing and running vehicle inspection and maintenance (I/M) programs . As well as distinguishing between basic and enhanced I/M programs, these guidelines must clarify how states are to meet other minimum design requirements set by the CAA. One such requirement that applies to both basic and enhanced I/M programs is the performance ofOnboard Diagnostic (OBD) system checks as part ofthe required, periodic inspection. On November 5, 1992, EPA published the I/M rule to meet most ofthe above-referenced CAA requirements . At the time the I/M rule was promulgated, however, federal OBD certification standards had not been published. To address the CAA' s OBD-1/M requirement, EPA reserved sections in the 1992 rule, with the understanding that these reserved sections would be amended at some future date. Although the federal requirement to incorporate OBD into new vehicles began with the 1994 model year (MY), manufacturers were allowed to request waivers on vehicles for MY 1994-95, so full compliance was not required on all light-duty cars and trucks sold in this country until MY 1996. On August 6, 1996, EPA published amendments to the 1992 I/M rule establishing OBD-1/M requirements for I/M performance standards and I/M State Implementation Plans (SIPs) . The 1996 amendments also specified data collection, analysis, and summary reporting requirements for the OBD-I/M testing element; established OBD test equipment requirements and the OBD test result reporting format; and identified those conditions that would result in an OBD-1/M pass, failure, or rejection. Lastly, the August 6, 1996 amendments revised 40 CFR part 85, subpart W to establish OBD-1/M as an official performance warranty short test under section 207(b) ofthe Act. At the time the original OBD-1/M requirements were established, it was not practical to evaluate the real-world, in-use performance ofOBD because the vehicles in question were still too new and the number ofthose vehicles in need ofrepair were too few to make pilot testing worthwhile. Therefore, in 1998, EPA further amended its OBD-I/M requirements to delay the date by which I/M programs must begin OBD testing to no later than January 1, 2001. One ofthe primary reasons for delaying the deadline for beginning OBD-I/M testing was to give EPA time to evaluate the OBD check as an I/M program element and to give states time to prepare for implementation. In 

### conducting its evaluation ofOBD, however, EPA found that identifying and recruiting OED-equipped vehicles in need ofrepair proved more difficult and time-consuming than originally anticipated. As a result, EPA has only recently completed the assessment ofOBD-1/M effectiveness and implementation issues referenced in this guidance. 

### 2

### During the course ofthis evaluation, however, it became clear that certain regulatory changes were needed to . ensure the smooth implementation ofOBD-1/M testing by the states. In response to its findings on OBD effectiveness and its study ofthe various implementation issues associated with OBD-1/M testing, EPA has amended the OBD-1/M testing requirements by publishing a final rulemaking (FRM) in the Federal Register on April 5, 2001 1• 

### The goal ofthese amendments is to update and streamline requirements and to remove regulatory obstacles that may otherwise impede the effective implementation ofOBD-1/M testing. Among other things, the revised requirements : 1) provide states several options for extending the current deadline for mandatory implementation ofthe OBD-1/M inspection beyond January 1, 2001; 2) clarify states' options regarding the integration ofOBD-1/M checks into existing l/M networks; 3) revise and simplify the current list ofDiagnostic Trouble Codes (DTCs) that constitute the OBD-1/M failure criteria to include any DTC that leads to the dashboard Malfunction Indicator Light (MIL) being commanded on; and 4) provide for exemptions from specific readiness code rejection criteria on OED-equipped vehicles based upon vehicle model year. In addition to the above cited regulatory revisions, EPA believes it is important to respond to states ' requests to provide additional guidance on how to successfully implement OBD-1/M testing in an l/M program. EPA is therefore issuing this guidance at this time in response to those requests and to assist those states and local areas that are considering or planning early implementation ofOBD checks as part oftheir l/M programs . Scope of Guidance This guidance incorporates several key recommendations made to EPA by the OBD Workgroup, which is part ofthe Mobile Source Technical Review Committee, established under the Federal Advisory Committee Act (FACA). This guidance was also developed by drawing from the experiences of several states that are currently performing some form ofOBD-based inspection. As ofthis writing, ten states (New York, Califomia2, Colorado, Alaska, Illinois, Wisconsin, Vermont, Oregon, Maine, and Utah3) 

### are performing some form ofvehicle OBD system check and at least three other states (Indiana, New Hampshire, and Georgia) are actively moving towards early implementation ofvehicle OBD system checks. Lastly, the development ofthis guidance was aided by comments received from stakeholders in response to an earlier, draft guidance released for public comment in December 2000.

1 Copies ofthe FRM are available via the Internet at www.epa.gov/oms/epg/regs .htm. 2 Currently, California and New York are performing only a visual check for MIL illumination. A scanner check for trouble codes will be added in the future. 3 In Utah, the l/M program is administered at the county level (as opposed to at the state level). Although there are several counties in Utah currently required to implement U M, only one county - Davis - has opted to begin early implementation ofthe OBD-1/M check. 

### 3This guidance reflects EPA's current understanding ofthe challenges and issues unique to the performance ofOED testing in the 

### VM program environment, and includes our recommendations for how best to address those issues at this time. As is the case with any technology-driven pollution control measure, our understanding ofthe issues and the issues themselves are likely to change over time as we gain more experience with them. Therefore, EPA will update this guidance from time to time, as developments warrant. To ensure that this document is updated accurately, EPA invites those involved with performing the OED-VM check to share information with us by contacting Ed Gardetto at 734-214-4322, or via e-mail at gardetto.edward@epa.gov. Program data, recommendations, and other forms offeedback relevant to the performance ofthe OED-VM check can also be sent to: Ed Gardetto c/o U.S. Environmental Protection Agency 2000 Traverwood Drive Ann Arbor, MI 48105 Lastly, this guidance does not address those 

### VM implementation issues which are common to all test types and for which there are no unique, OED-specific considerations . For example, this guidance does not address geographic coverage requirements or the adequacy of program funding mechanisms. Readers can find EPA's requirements and/or recommendations for these generic 

### VM implementation issues by consulting the 

### VM rule (as amended) and EPA's subsequent 

### VM policy documents, which are available via the Office ofTransportation and Air Quality (OTAQ) web site at: http:\\www.epa.gov\otaq\im.htm. 

### Vehicle OBD System Checks: Basic Requirements Recommended Model Year Coverage Although some variety ofOED system has been an option on certain vehicle models since the early 1980's, standardized OED systems (also known as OED II) were not introduced until MY 1994, and such systems did not appear on all new light-duty vehicles sold in this country until MY 1996. Therefore, for 

### VM purposes, EPA does not require that pre-1996 MY vehicles be subject to the OED inspection discussed in this guidance. Furthermore, EPA does not recommend that such testing include MY 1994-95 vehicles because not all such vehicles are OED-equipped and the availability to manufacturers oflimited waivers from some OED requirements makes determining which ofthese vehicles to test (and to what standards) administratively very difficult. Additionally, EPA's MOEILE6 emission factor model will not provide emission reduction credit for the performance ofOED-VM checks on pre-1996 MY vehicles. EPA also does not recommend that vehicles older than MY 1994 be subjected to OEDbased 

### VM testing, even ifit is determined that the vehicle is equipped with an OED computer, 4and may even have a malfunction indicator light (MIL) illuminated. The reason we do not recommend performing an OBD-VM scan on pre-1994 MY OED-equipped vehicles is because such vehicles use an earlier, non-standardized generation ofOBD system (also known as OBD I). Due to the lack offederal standards for OBD I systems, the systems themselves tend to be proprietary and may not be compatible with the standardized OBD II scanners that will be used in most 

## IiM programs4 • Elements ofan OBD-VM Check An OBD-VM check consists oftwo types ofexamination: A visual check ofthe dashboard display function and status (also known as the MIL and/or bulb check) and an electronic examination ofthe OBD computer itself. These two examinations, taken together, comprise the seven step procedure outlined below. 1) Initiate an official test by scanning or manually inputting the required vehicle and owner information into the reporting medium (i.e., PC-based electronic reporting system or manual test report) . 2) Visually examine the instrument panel to determine ifthe MIL illuminates briefly when the ignition key is turned to the "key on, engine off' (KOEO) position. A briefperiod ofillumination ofthe MIL at start-up is normal and helps confirm the bulb is in proper, operating condition. This portion ofthe test procedure is also known as the "bulb check." Enter the results ofthe bulb check into the reporting medium. 3) Locate the vehicle's data link connector (DLC) and plug a scan tool into the connector. While it is recommended that this step be performed with the ignition in the "off" position, this step can also be performed with the ignition running. Given the variety oflocations manufacturers have chosen in practice, locating the DLC may well be the most time-consuming element ofthe inspection. We will discuss the issue ofatypical DLC location elsewhere in this guidance. 4) Start the vehicle's engine so that the vehicle is in the "key on, engine running" (KOER) condition5

. The MIL may illuminate and then extinguish during this phase. Continued illumination while the engine is running is cause for failure .

4 40 CFR 85.2222 "On-board diagnostic test procedures" requires that the scan tool used for the 080-UM inspection be capable ofcommunicating with the OBD system in compliance with the Society ofAutomotive Engineers (SAE) Recommended Practice J1979. 5 While it is possible to perform the electronic scan portion ofthe OBD-1/M check in the KOEO position for most vehicles, EPA discourages this practice because it can lead to false failures for some makes and models ofvehicles (such as MY 1996-2001 Subarus). 5

### Also, ifthe MIL illuminates during this phase but was not observed in step 2, the vehicle should not be failed for step 2. 5) With the scan tool in the "generic OBD" mode, follow the scan tool manufacturer's instructions 6 

### to determine: • Vehicle readiness status7 

### • MIL status (whether commanded on or off)8, and Diagnostic Trouble Codes (DTCs) for those vehicles with MILs commanded on9 • 

### 6) Record the results ofthe OBD inspection in the appropriate medium. Depending upon the design and feature requirements ofthe program, this may be an automated process. 7) Without clearing DTCs or readiness codes, turn offthe vehicle ignition, and then disconnect the scan tool 10. 

### Clearing codes - ifsuch is necessary- should be reserved for the repair portion ofthe program (even though in test-and-repair programs, the same personnel may be engaged in both activities). These codes (and the associated "freeze-frame" data) are important for the performance of proper diagnostics prior to repair. Although the above inspection elements are listed sequentially, current regulations do not specify the sequence that must be followed in performing the OBD-I/M inspection, and EPA sees no reason for applying a rigid sequence at this time. 

### In some cases it may make more sense to

6 For UM purposes, the inspectors and repair technicians should be advised to conduct the scan in "generic" mode as opposed to a vehicle manufacturer specific mode. EPA is aware ofsome instances in which using a scan tool in the vehicle manufacturer specific mode will result in confusing or misleading readings regarding vehicle readiness . 7 Refer to SAE Jl979 MODE 01PIO01 DATA C and D. 8 Refer to SAE Jl979 MODE 01PIO01 DATA A BIT 7. 9 EPA's original OBD-1/M failure criteria were limited to power-train, emission-related DTCs (refer to SAE JI 979 MODE 03). In its April 5, 2001 rulemaking, however, EPA simplified the failure-triggering OTC criteria to any OTC that leads to the MIL being commanded on. As part ofits technical support efforts for the April 5, 2001 rulemaking, EPA looked at six months' worth ofOBD-1/M data from the Wisconsin I /M program and found that less than 0.5% ofthe OBD-equipped vehicles tested during that period experienced Mils being commanded on for DTCs falling outside the previous failure criteria. As a result, EPA does not believe the simplified failure criteria will result in higher overall l/M failure rates -- especially not in those areas that opt to replace existing tailpipe testing on MY 1996 and newer vehicles with the 080-1/M scan. IO For programs conducting both 080 and tailpipe testing on 080-equipped vehicles, the tailpipe test may be conducted prior to this step, to avoid an extra, unnecessary key-off , key-on cycle. 

### 6

### conduct the visual portion ofthe inspection after performing the onboard computer scan. For example, a state choosing to perform both a traditional tailpipe test and the OBD-1/M check on OED-equipped vehicles may choose to reduce the overall test time involved by conducting the OBD scan at the same time the other test is performed. EPA has found that a scan tool can be plugged into a still-running vehicle without producing erroneous readings. Therefore, we believe states should be allowed the flexibility to determine the optimum test sequence to meet their programmatic needs. However, EPA does caution that unforeseen problems may arise with some subset ofthe fleet due to changes in the sequence. EPA therefore asks that states consult with the Agency should they find unusual failure patterns among certain makes and models ofvehicles in conjunction with the use ofalternative test sequences. For readers who prefer their information presented graphically, a flowchart ofan acceptable OBD system check is included in Appendix E ofthis guidance document. It 

### was developed by the Center for Automotive Science and Technology at Weber State University, and is consistent with EPA guidance. Basis for Failure or Rejection Unless otherwise noted in this guidance, a vehicle should be failed for any ofthe following five reasons, with the exception ofthe last (for which the appropriate action is rejection): 11 

### 1) It 

### is a 1996 or newer vehicle and the data link connector (DLC) is missing, has been tampered 12 

### with, or is otherwise inoperable. (Action: Failure) 2) The MIL does not illuminate at all when the ignition key is turned to the KOEO position. The MIL should illuminate (on some vehicles, only for a briefperiod of time) when the ignition key is turned to the KOEO position. (Action: Failure) 3) Ifthe MIL illuminates continuously or flashes after the engine has been started, even ifno fault codes are present, since this could indicate a serial data link

11 States should be aware that some vehicles have atypical OBD configurations, and should take steps to avoid unfairly penalizing motorists. For example, states may incorrectly suspect motorist tampering for those vehicles that are manufactured with the DLC in a hard-to-find location. EPA is working with manufacturers, operating OBD-1/M programs, and Weber State University to develop an online clearinghouse ofOBD-related information useful to state UM programs and other stakeholders, including all OBD-related Technical Service Bulletins (TSBs) from the manufacturers and all relevant updates. See Appendices B through D for more information on vehicles with atypical OBD system issues. 12 Tampering is considered to be any modification ofthe vehicle that deviates from the certified configuration ofthe vehicle, particularly ifsuch modification has the practical effect ofmaking the vehicle untestable (by, for example, making the DLC inaccessible) or otherwise constitutes an attempt to evade the program (by, for example, using illegal aftermarket devices designed to circumvent the OBD computer or provide false results during an OBD-UM check). Under this definition, moving a DLC as part ofcollision repairs would not necessarily constitute tampering -- provided the DLC was not hidden or rendered otherwise inaccessible as a result ofbeing moved. 

### 7

### failure. 13 

### (Action: Failure) 4) Any DTCs are present and the MIL status, as indicated by the scan tool, is commanded on, regardless ofwhether or not the MIL is actually illuminated. Do not fail the vehicle ifDTCs are present and the MIL status, as indicated by the scan tool, is off, because such non-MIL-triggering DTCs are considered "pending" and frequently selfclear without requiring repair ofthe vehicle. MIL command status must be determined with the engine running. (Action: Failure) 5) The number ofOBD system monitors showing a "not ready" status exceeds the number allowed for the model year in question. (Action: Rejection) 14 

### Table 1 below lists the possible test outcomes in tabular form. Table 1 - Possible OBD-1/M Outcomes Vehicle Passes If: * Bulb check OK and *MIL not lit while engine running and * MIL not commanded on for any DTCs and * All required readiness codes are set Vehicle Fails If: * Bulb check not OK and/or * MIL lit while engine running and/or * MIL commanded on for any DTC and/or * DLC missing, tampered, or inoperable Vehicle Rejected If: * More unset readiness codes found than allowed based on MY and/or * DLC cannot be located or is inaccessible

13 States should be aware that some vehicles will illuminate a MIL when a scan tool is connected and the vehicle is still in the "key on, engine off' condition. In some cases, the scan tool will indicate that the MIL is, in fact, commanded on -- even though no DTCs may be present. EPA has found that these vehicles will usually extinguish the MIL and remove the "MIL commanded on" indicator when the engine is started. To avoid falsely failing vehicles, therefore, it is important that the electronic portion ofthe OBD-I/M check be conducted only with the vehicle in the "key on, engine running" condition (as indicated in the test procedure described above). 14 Although earlier requirements stipulated that OBD-equipped vehicles be rejected from further testing ifany monitor was "not ready," EPA has revised these readiness criteria to allow states to not reject MY 1996-2000 vehicles with two or fewer unset readiness codes, or MY 2001 and newer vehicles with no more than one unset readiness code. The complete MIL check and scan should still be run in all cases, however, and the vehicle should still be failed ifone or more DTCs are set and the MIL is commanded on. The vehicle should also continue to be rejected ifthe OBD computer does not set readiness codes for 3 or more monitors on MY 1996-2000 vehicles, or two or more monitors on MY 2001 and newer vehicles. Readiness codes in general, and the specific codes and conditions covered by the April 5, 2001 amendments will be discussed in more detail under a separate section ofthis guidance. 8

### l/M-Related DTCs Until recently, Federal l/M regulations identified a subset ofpower train (or P-code) DTCs as being relevant for l/M purposes. 

### Ifa vehicle was identified through an l/M program as having a MIL commanded on for one or more ofthose P-codes, then Federal regulations required that the vehicle fail the inspection. In 

### an attempt to simplify these failure criteria - and to harmonize Federal requirements with California Air Resources Board (CARB) requirements -EPA amended this requirement as part ofits April 5, 2001 rulemaking. Under the revised failure criteria, a vehicle shall now be failed for the presence ofany DTC that results in the "Check Engine" MIL being commanded on. In 

### commenting on an earlier draft ofthis implementation guidance, several commenters raised concerns that EPA's simplified failure criteria would result in vehicles being failed for non-emission related components or systems, such as the brakes or suspension. Although some vehicle onboard computers may monitor non-emission-related components and systems at the manufacturer's discretion, Federal regulations require that the "Check Engine" MIL only be illuminated for emission-related malfunctions. Other dashboard lights may be illuminated to indicate the need for service ofa non-emission-related component or system, but the presence ofsuch lights does not constitute grounds for failing the OBD-1/M check. Furthermore, EPA has examined data from over 300,000 OBD-1/M checks performed in actual l/M lanes and has not found a single instance ofthe simplified failure criteria leading to the failure ofa vehicle for a non-emission-related component or system. EPA also wants to acknowledge that it is possible we may need to limit the criteria for failing OBD-equipped vehicles after such vehicles reach an as-yet undetermined age and/or mileage. The reason for considering this possibility stems from the fundamental difference between how OBD triggers repairs versus how traditional tailpipe tests trigger repairs. Traditional l/M tailpipe tests identify a vehicle as failing for a given pollutant through direct sampling ofthe exhaust plume. These tests vary in the degree to which they provide any additional information that can be used to target the component or system failure that has led to the high emission reading. In 

### such programs, repair technicians have a fair degree ofdiscretion when it comes to recommending repairs to address a given failure, although owners are protected from excessive economic hardship by the cost waiver option. OBD, on the other hand, identifies specific components and/or systems in need ofrepair or replacement. As a result, EPA foresees the possibility that some advanced-aged OBD-equipped vehicles could be failed for DTCs for which the only available repair option would cost substantially more than the fair market value ofthe vehicle itself . Under such a scenario, the waiver option does not offer much consumer protection, since such repairs tend to be all-or-nothing propositions. For example, a motorist faced with a transmission repair cannot reasonably opt to have the transmission "halffixed" to take advantage ofthe cost waiver option. Given the relative newness ofOBD II, EPA has not been able to gather the data 9necessary to determine whether situations like the one above will actually happen in practice (though the Agency certainly plans to gather such data in the future). We do believe however that program requirements should be reasonable, and that the economic burdens ofa program should be balanced by the environmental benefit likely to result from the imposition ofthose burdens . Therefore, we may revise our failure criteria at some future date, once data has been gathered and analyzed concerning the actual costs associated with repairing high mileage/age OED-equipped vehicles across the full range ofpossible MIL-triggering DTCs. Test Report 

### Ifa vehicle fails, the test report given to the motorist should include the status ofthe MIL illumination command and the alphanumeric fault code(s) listed along with the DTC definition(s) as specified per SAE 12012and11930. Only the fault codes leading to the inspection failure should be listed on the report given to the motorist. EPA makes this recommendation because it is possible that an OBD system may set DTCs without commanding a MIL to be illuminated. These DTCs usually reflect an intermittent condition which may or may not be a problem at the time oftesting. 

### Ifthe condition does not recur within a certain number oftrips, the code will eventually be cleared; ifthe condition does recur, the system may then determine that a MIL should be illuminated. Therefore, no DTCs should be printed on test reports for vehicles that pass the inspection. An owner who receives notice ofthese codes on the same sheet ofpaper with notification ofpassing the state inspection may become confused or desensitized to the importance ofDTCs and the MIL. Lastly, unset readiness codes should also be listed on the report 

### ifthe number ofunset readiness codes exceeds the limit for which an exemption is allowed (i.e., ifthe outcome ofthe test is rejection based upon the presence of too many unset readiness codes). 

### Ifthe number ofunset readiness codes falls below the limit for which an exemption is allowed (and the vehicle would otherwise pass the inspection) then no unset readiness codes should be listed on the test report provided to the motorist. Readiness Status : Initial Test The OBD system monitors the status ofup to 11 emission control related subsystems by performing either continuous or periodic functional tests ofspecific components and vehicle conditions. The first three testing categories - misfire, fuel trim, and comprehensive components - are continuous, while the remaining eight only run after a certain set of conditions has been met. The algorithms for running these eight, periodic monitors are unique to each manufacturer and involve such things as ambient temperature as well as driving conditions. Most vehicles will have at least five ofthe eight remaining monitors (catalyst, evaporative system, oxygen sensor, heated oxygen sensor, and exhaust gas recirculation or EGR system) while the remaining three (air conditioning, secondary air, and heated catalyst) are not necessarily applicable to all vehicles. When a vehicle is scanned at an OBD-I/M test site, these monitors can appear as either "ready" (meaning the monitor in question has been evaluated), 10

### "not ready" (meaning the monitor has not yet been evaluated), or "not applicable" (meaning the vehicle is not equipped with the component monitor in question). There are several reasons why a vehicle may arrive for testing without the required readiness codes set. These reasons include the following: 1) Failure to operate the vehicle under the conditions necessary to evaluate the monitor(s) in question; 2) A recent resetting ofthe OBD system due to battery disconnection or replacement, or routine maintenance immediately prior to testing 15 ; 

### 3) A unique, vehicle-specific OBD system failure; 4) An 

### as-of-yet undefined system design anomaly; or 5) A fraudulent attempt to avoid 

### IfM program requirements by clearing OBD codesjust prior to OBD-J/M testing (by, for example, temporarily disconnecting the battery). 

### In addition to the above considerations, EPA has also found that a small number of vehicles may be flagged as "not ready" or "not supported" for one or more ofthe continuous monitors (i.e., misfire, fuel trim, and/or comprehensive components). This makes no sense because continuous monitors are designed to run continuously (as their name implies) and therefore should always be flagged as "ready." 

### In its investigation ofthis issue, EPA has determined that the problem is the result ofincompatibility between the vehicle and scanner software and is not indicative ofa fault with the vehicle's OBD system. As a result ofthis discovery, EPA recommends that programs disregard these continuous monitors when establishing the readiness status ofthe vehicle. This exclusion is for readiness determination purposes only; a vehicle with a MIL commanded on for a continuous monitor based DTC should continue to be failed in compliance with the test procedure discussed earlier in this guidance. EPA is working with state programs and OBD software suppliers to address this issue and will issue revised guidance as warranted. Because the presence ofunset readiness codes among the non-continuous monitors could be a sign ofattempted fraud, it is important that all OED-equipped vehicles be checked to confirm that readiness codes have been set as one ofthe pre-requisites for a valid OBD-I/M inspection. Nevertheless, as described in the FRM, EPA also believes that the previous requirement regarding readiness codes (i.e., that a vehicle be rejected from further testing ifany monitor is found to be "not ready") was more rigorous than either necessary or practical. Therefore, as discussed under "Basis for Failure or Rejection" above, EPA has revised the

15 As part ofa program's outreach effort, car owners should be advised to allow for approximately one week ofnormal vehicle operation after repairs and prior to OBD-UM testing (or retesting) . 

### 11

### readiness requirement so as to allow states to complete the testing process on MY 1996-2000 vehicles with two or fewer unset readiness codes; for MY 2001 and newer vehicles, the testing process can still be completed provided there is no more than one unset readiness code. This does not mean that these vehicles are exempt from the OBD-I/M check16• 

### The complete MIL check and scan must be run in all cases, and the vehicle still must be failed ifany ofthe failure criteria discussed in this guidance are met. The vehicle should continue to be rejected ifit is MY 1996-2000 and has three or more unset, non-continuous readiness codes or is MY 2001 or newer and has two or more unset, non-continuous readiness codes. As discussed in the Technical Support Document for the FRM, this amendment is based upon EPA's findings regarding readiness codes from Wisconsin's OBD-1/M data and also reflects a FACA workgroup recommendation. Since August 1998, Wisconsin's l/M program contractor has been sending to EPA OBD scanning and IM240 test results data collected on MY 1996 and newer vehicles coming through the Wisconsin I/M test lanes. In 

### analyzing the Wisconsin data, EPA made the following observations regarding the readiness status ofthe OED-equipped vehicles presented for testing 17 : 

### • The majority ofvehicles showing up at the I/M lane with readiness codes reading "not ready" were from MY 1996; the "not ready" rate for MY 1996 vehicles was 5.8%. • The frequency ofvehicles with readiness codes reading "not ready" dropped offwith each successive model year - to 2.2% for MY 1997 and 1.4% for MY 1998. • Ifan exemption were allowed for up to two readiness codes to read "not ready" before a vehicle would be rejected from further testing, the rejection rate drops - to 2.2% for MY 1996 and to 0.2% for MY 1997 and MY 1998, for a three model year average of0.9%. The intention behind EPA's decision to allow limited exemptions from the readiness

16 As discussed above, when determining the readiness status ofa vehicle, EPA recommends that programs only consider the non-continuous monitors. Likewise, in assessing whether a "not ready" vehicle can be exempt from the readiness rejection requirement based upon the number ofunset readiness codes present, only unset readiness codes among the noncontinuous monitors should be counted. 17 In commenting on an earlier draft ofthis implementation guidance, some commenters suggested that EPA's figures regarding the frequency of"not ready" vehicles in the in-use fleet are skewed downward because the Agency's data comes from a program where the OBD-1/M check is being performed on an "advisory only'' basis. These commenters argued that in an "advisory only" program motorists had no incentive to fraudulently clear M!Ls by disconnecting the battery since there was no negative repercussion from showing up for the inspection with a lit MIL. These commenters further argued that once motorists began failing based upon M!Ls, the frequency ofvehicles with unset readiness codes at the time ofthe initial test would go up. To test this hypothesis, EPA has begun analyzing program data from the Oregon OBD-1/M program, which is currently failing vehicles based upon the results ofthe OBD-1/M check. Based upon a preliminary analysis ofthe Oregon data, EPA has found that roughly 1.4% ofMY! 996+ vehicles are being rejected at the time ofthe initial test due to an excessive number of"not ready" codes (assuming the readiness exemption allowance provided by the April 5, 2001 FRM). 

### 12

### rejection criteria is exclusively to avoid inconveniencing motorists on the basis ofvehicle conditions that are beyond their control, that are currently the subject ofdiscussion between EPA and various manufacturers, and that, in some cases, may result in potential enforcement action. The purpose ofthe limited readiness exemption is not to relieve manufacturers oftheir responsibility to design and market OBD systems that comply with existing OBD certification requirements 18• 

### Nothing in this guidance in any way changes or otherwise impacts these obligations on the part ofvehicle manufacturers . In 

### fact, EPA has already initiated several investigations which may result in enforcement actions related to these requirements. Because ofthe small number ofvehicles involved, EPA believes that the environmental impact ofthe limited readiness exemption will be negligible, especially given the likelihood that at least some ofthese readiness codes will have been set in time for subsequent 

### OBD-VM checks, and the fact that an unset readiness code is not itselfan indication ofan emission problem. EPA believes that allowing limited exemptions from the readiness code requirement as described above makes the most sense at this time, while EPA, CARB , and the manufacturers work to clarify system function requirements with regard to 

### VM. Lastly, EPA does not believe that allowing these limited exemptions will interfere with the use ofreadiness codes to help deter possible fraud because such fraud would inevitably lead to more monitors being set to "not ready" than are allowed under EPA's limited exemptions. In 

### addition to the above exemptions, EPA also recommends that 

### VM programs waive the readiness requirement or otherwise accommodate specific makes, models, and model years ofvehicles with known readiness design problems, in accordance with applicable technical service bulletins and/or EPA guidance. EPA has compiled a list of such vehicles and included it in Appendix D. Even with these vehicle-specific accommodations and the above exemptions, however, some vehicles will still need to be rejected based upon readiness code status. In 

### the case ofa vehicle rejected for unset readiness codes (which does not otherwise meet the failure criteria described in this guidance), the motorist should be given the option ofoperating the vehicle for a week under normal operating conditions in an attempt to evaluate the necessary monitors without being required to visit a repair facility prior to retesting. Ifthe monitors still have not performed an evaluation by the first retest, the motorist should then be advised to visit a repair

18 To help emphasize this point, EPA clarifies here that the obligations ofthe automobile manufacturers with regard to OBD equipment are specified in regulatory section 40 CFR 86.094-l 7(e)(l): "Control ofAir Pollution From New Motor Vehicles and New Motor Vehicle Engines: Regulations Requiring On-Board Diagnostic Systems on 1994 and Later Model Year Light-Duty Vehicles and Light-Duty Trucks," which imposes, among other things, the obligation to design, build and certify OBD systems that: "record code(s) indicating the status ofthe emission control system. Absent the presence ofany fault codes, separate status codes shall be used to identify correctly functioning emission control systems and those emission control systems which need further vehicle operation to be fully evaluated." In promulgating these requirements on February 19, 1993 the Agency stated: 'The readiness code will ensure l/M testing personnel and service technicians that malfunction codes have not been cleared since the last OBD check ofthe vehicle's emission-related control systems. This code will be essential ... since l/M personnel must be sure that the OBD system has sufficient time to completely check all components and systems. The readiness code is also crucial for indicating to service personnel whether any repairs have been conducted properly." 13facility where the monitors can be set based upon vehicle-specific, manufacturer guidance. Alternatively, states may decide to allow such vehicles to default back to the traditional I/M tests performed on the vehicles in question prior to introduction ofthe OBD-VM test requirement. EPA recommends that states that choose to use back-up tailpipe testing in lieu of rejection track this activity carefully to ensure that the practice does not lead to an inadvertent loophole through which motorists routinely avoid the OBD-1/M inspection in favor ofthe tailpipe test. In all cases, it is important to emphasize that lack ofreadiness is a special status particular to OBD systems and that the vehicle is not necessarily producing excess emissions. Instead, the vehicle's emissions status is officially "Unknown," due to a failure to meet certain monitoring conditions prior to the inspection. In order to minimize confusion, EPA recommends that states provide a written statement about OBD and readiness status to motorists who are rejected based upon an excessive number ofunset readiness codes. Such a statement should make the following key points: 1) A vehicle rejected as "not ready" is not necessarily " dirty. " 2) "Not ready"just means the vehicle's computer has not had an opportunity to fully evaluate the vehicle's performance. 3) Many circumstances can lead to a vehicle being "not ready," including recent vehicle repairs and/or battery replacement. 4) In most cases, a week' s worth ofcontinued vehicle operation under normal operating conditions will be sufficient to make a "not ready" vehicle "ready." 5) In a very limited number ofcases (less than 1% ), a "not ready" vehicle may need to be taken to a repair facility, where the readiness codes can be set based upon vehicle-specific, manufacturer guidance. Readiness Status : Retest After Repairs -- Non-catalyst-related DTCs OBD-1/M programs also must address the readiness code status ofvehicles returning for retesting after repairs have been performed to correct an initial OBD-VM failure. Even ifthe vehicle showed all readiness codes as "ready" on the initial test, vehicles returning to the I/M lane immediately following repair will likely havejust had the fault code memory cleared by the repair technician (the proper step following a repair). Upon clearing the fault code memory, however, all readiness codes will also be cleared and set to "not ready." 

### Ifthe vehicle returns for retesting immediately after repair, it is possible that one or more readiness codes will register as "not ready. " To address this possibility, EPA recommends that the vehicle be held to the same readiness criteria as are applicable for an initial test (i.e., ifthe vehicle is MY 1996- 142000, a maximum ofany two unset readiness codes may be allowed, while for MY 2001 and newer vehicles, no more than one unset readiness code is allowed). To help minimize the potential for vehicles showing up for their retest with an excessive number ofunset readiness codes, outreach to the repair community should stress the importance ofconfirming vehicle readiness prior to returning a repaired, OED-equipped vehicle to its owner. Motorists should also be informed that they should plan to allow a week's worth of ordinary driving between receiving repairs and getting a vehicle retested, to avoid being rejected based upon an excessive number ofunset readiness codes. If, despite these caveats, a vehicle is presented for retesting with an excessive number ofunset readiness codes after repair, EPA believes that the submission ofrepair receipts as proofofrepair is an adequate method for establishing that the necessary repairs have been performed. EPA appreciates that the ability of inspectors to confirm repairs prior to retesting will vary, depending upon whether the 

### VM program is a test-and-repair or test-only program. In the case oftest-only programs, outreach efforts to the repair community should stress the importance ofincluding an indication on the repair receipt that the repairs in question are OED-related (i.e., by including the diagnostic scan in an itemized list ofservices performed). A repair receipt (as opposed to a repair estimate) including evidence ofa diagnostic scan and dated either on the same day as the initial test or sometime thereafter may be considered adequate for establishing proof-of-repair for retest purposes in test-only programs. In the case ofowner-performed repairs, the program should require the submission ofappropriately dated parts receipts prior to retesting, and these receipts should be reviewed by the test station manager, who in tum should be trained to determine whether the parts in question are relevant to the cause offailure. EPA believes that the number ofvehicles falling into this last category (i.e., OED-equipped vehicles that fail the initial test and return for retesting with owner-performed repairs and an excessive number ofunset readiness codes) should be relatively small 19• In commenting on an earlier draft ofthis implementation guidance, some commenters raised concern that it would be possible for repair technicians to selectively clear DTCs without performing repairs and without setting the remaining monitors (i.e. , those without DTCs recorded) to "not ready." Ifthis were possible -- the commenters argued -- then vehicles that should be failed could be fraudulently passed on the retest (even without receiving repairs) because ofthe readiness exemptions allowed by EPA (assuming the number ofDTCs resulting in the initial failure did not exceed the number ofreadiness exemptions allowed for the model year in question) . In reality, it is not possible to selectively clear DTCs or to only set some readiness monitors to "not ready" while leaving the remaining monitors "ready." As currently designed, the feature which allows the clearing ofDTCs is an all-or-nothing proposition --

19 In looking at data from the Oregon OBD-1/M program, EPA has found that for the tailpipe test, the average number ofretests required before passing after the initial failure is 2.01 , while for vehicles failing the OBD-1/M check, the average number ofretests required before passing after the initial failure is 1.39 (even after accounting for the retest rejection rate associated with the readiness issue described in this section) .15specifically to avoid fraud such as that suggested by the commenters20 • Readiness Status : Retest After Repairs -- Catalyst-related DTCs (P0420 - P0439) Based upon an analysis ofdata from the Oregon OBD-1/M program EPA recommends that vehicles which fail the initial OBD test for any ofthe catalyst monitoring codes (P0420 through P0439) be held to a higher standard for the retest than is the case with other failure codes. EPA recommends that initial catalyst failures follow one ofthe following steps at the time ofretest: 1) 

### Ifthe catalyst monitor is "ready" at the time ofretest, then the vehicle should be treated like any other vehicle returning for retest after failing for any non-catalystrelated DTC . 2) 

### Ifthe catalyst monitor is "not ready" at the time ofretest, then the owner should be required to provide proofofrepair, or the vehicle should be required to pass a tailpipe test to verify catalyst function . 3) Alternatively, at the program' s discretion, ifthe catalyst monitor is "not ready" at the time ofretest, the vehicle should be rejected until the catalyst monitor has been set to "ready." Readiness Status: Continuous Monitors As previously mentioned, EPA has found that a small number ofvehicles may be flagged as "not ready" or "not supported" for one or more ofthe continuous monitors (i.e., misfire, fuel trim, and/or comprehensive components) . EPA recommends that programs exclude these continuous monitors from consideration when establishing the initial readiness status ofthe vehicle. This exclusion is for readiness determination purposes only; a vehicle with a MIL commanded on for continuous monitor based DTCs should continue to be failed in compliance with the test procedure discussed earlier in this guidance. EPA is working with state programs and OBD software suppliers to address this issue and will provide revised guidance as warranted. In the case ofvehicles which fail the initial OBD-1/M check exclusively for DTCs related to the continuous monitors, repair technicians should be instructed to not clear the DTCs electronically after performing the necessary repairs. Instead, the success ofrepairs based upon continuous monitor related DTCs should be confirmed by letting the OBD system detect the repair and reset itselfto "ready" (a process which should occur naturally after 3 engine key20 R efer to SAE J 1979 - "E/E Diagnostic Test Modes," Mode $04. 16on/key-offcycles, provided the repairs were performed correctly). In the case ofinitial failures for a mix ofcontinuous and non-continuous monitor related DTCs, the DTCs should continue to be cleared, post-repair, as recommended elsewhere in this guidance. Evaporative System Testing and OBD EPA's analysis ofthe Wisconsin 

### VM lane data suggests that OBD-I/M testing can be supplemented by including a separate gas-cap check. When EPA compared failure rates for the evaporative portion ofthe 

### OBD-VM test to the failure rate for the stand-alone gas cap test we found that the separate gas cap test was able to identify a substantial number ofleaking gas caps that were not identified by the OBD monitors due to the different failure thresholds. The seeming disparity described above is a result ofthe different detection thresholds for the two tests. The stand-alone gas cap test was designed to detect a leak as small as 60 cubic centimeters per minute (cc/min) at a pressure of30 inches ofwater, while OBD systems were designed to detect leaks equal to a circular hole 0.040 inches in diameter. The 0.040 inch hole equates to a flow rate in excess of2,600 cc/min at 10 inches ofwater column (i.e., the maximum allowable internal tank pressure using the enhanced evaporative emission test) 21 • As a result, an OBD system can reliably detect a loose or missing gas cap, while a properly tightened but leaking gas cap that can easily be identified by the gas cap test will probably not be identified by OBD. Since the gas cap test is able to identify an excessive emission condition not identified by OBD, EPA recommends including this additional testing element in those areas that need substantial reductions in hydrocarbon (HC) emissions from mobile sources as part oftheir ozone attainment plans. For states with more modest air quality needs with regard to mobile sources, EPA is leaving it to the states to assess their needs regarding whether or not gas cap testing is added to the OBD testing regime. EPA is reservingjudgement at this time because we still do not have sufficient data to draw reliable conclusions concerning the frequency of leaking gas caps in the in-use fleet. Our efforts in these areas have been complicated as a result ofpre-inspection replacement ofthe gas cap and, in some cases, a failure by inspectors to record the initial gas cap failure as a failure. During informal audits ofsuch programs, EPA has found that the faulty gas cap is frequently replaced on the spot, or the owner is directed to simply replace the cap later without being required to return for a retest22•

21 During its pilot testing ofOBD evaporative monitor effectiveness, EPA found that some in-use OBD systems were capable ofdetecting leaks from holes as small as 0.020 inches in diameter. A 0.020 inch hole equates to 600 cc/min at 10 inches ofwater column pressure. 22 EPA encourages states conducting the gas cap pressure check to stress the importance ofperforming and recording the results ofthe gas cap test accurately as part oftheir on-going outreach, training, and enforcement activities. 17Implementation Issues for Centralized vs. Decentralized OBD-Based Testing While EPA recommends that l/M programs integrate OBD-1/M test procedures into an overall, PC-based, real-time data-linked testing system, we understand that some programs which do not currently require test stations to be linked to a real-time database may opt to use generic, stand-alone, handheld scanners that do not generate automatic test reports and are not tied to a real-time data-linked system. While the use ofstand-alone scanners is not barred by l/M regulations for those areas not otherwise required to employ a real-time database, EPA nevertheless sees several drawbacks to the stand-alone approach to OBD-1/M testing. For example, the lack ofa real-time data link will mean that program oversight will necessarily be more costly, more labor intensive, and also less comprehensive, leaving the program perhaps more vulnerable to fraud. This decrease in program oversight effectiveness would come at a time when a significant portion ofthe program itselfis reverting to what is, in effect, a manual test program, where test reports are filled out by hand from information read offa handheld scanner's screen. Historically, programs that rely upon a non-automated process for making pass/fail decisions have been found to be even more difficult to oversee than traditional decentralized programs, since no electronic record is produced, making auditing more difficult. Furthermore, the use ofcomputer matching to identify noncomplying vehicles would be seriously restricted under such a system, assuming that such a system would not result in an electronically searchable testing database. And while it is possible that manually-completed test reports could be made computer-scannable and collected during site visits or sent to the state, the inherent time lag between the test and inclusion in the state database makes this a challenging implementation issue (i.e., a negative hit could equal data lag, not necessarily non-compliance). Lastly, the individual station's access to extensive and important program information (for example, DLC location databases and technical service bulletins regarding program updates, pattern failures , etc.) would be limited, both in terms ofavailability and timeliness. At a minimum, EPA believes that for an OBD-1/M test program to be most effective -

- whether centralized or decentralized -- it should be designed in such a way as to allow for: Real-time data link connection to a centralized testing database; Quality-controlled input ofvehicle and owner identification information (preferably automated, for example, through the use ofbar code) ; and Automated generation oftest reports. OBD and Inspector Fraud As is the case with all other l/M test types, the OBD-1/M check is vulnerable to inspector fraud, and program managers need to be on guard to limit the opportunities for this 18kind ofactivity. For example, it is currently possible for an unscrupulous inspector in a tailpipe-based program to engage in a practice known as "clean piping," where a knownclean vehicle is tested while the vehicle identification information for another (presumably dirty) vehicle is entered into the test record. Similarly, there is a limited opportunity for an inspector to "clean scan" an OED-equipped vehicle, but there are also methods for keeping this type ofactivity in check. The opportunity for "clean scanning" exists because the vehicle identification number (VIN) is not currently included in the data stored in the vehicle's onboard computer. Unlike "clean piping," however (where almost any known-clean vehicle will do), the opportunity for large-scale "clean scanning" can be greatly reduced through the use ofidentity-limiting information which is currently available from the vehicle's OED system. For example, programs could tally the number ofParameter Identifications (PIDs) 23 supported by the vehicle, which can be used as a check against the other vehicle information entered into the test record. Another important number to capture and track for quality control purposes is the Powertrain Control Module (PCM) diagnostic address24 • While these numbers do not identify a vehicle down to the level ofan individual registration and owner, they do allow for the separation ofvehicles into different makes, models, and engine families. Put another way, the PID count and PCM diagnostic address for a Honda Accord will be different from that ofa Ford Escort. Therefore, programs can limit the potential for fraud via "clean scanning" by comparing the PID count and/or the PCM diagnostic address to the other vehicle information in the test record. EPA is working with manufacturers and states currently implementing the OED-1/M inspection to gather the data necessary to interpret PID count and PCM diagnostic address information so it can be used for this purpose. In commenting on an earlier draft ofthis implementation guidance, some commenters suggested that even though the use ofPID counts and PCM diagnostic addresses could limit the potential for fraud via "clean scanning" among garages and service stations, it does not pose much ofa deterrent for dealerships, which have a readily available supply ofvehicles of the same make and model as vehicles being tested. While this may be the case, EPA does not believe that the potential for fraud among OED-equipped vehicles is any higher than the current potential for fraud via clean piping. Furthermore, ifa state is concerned that dealerships pose a greater fraud threat than other service providers, the state certainly has the discretion to monitor the compliance ofthose dealerships and take appropriate enforcement action, should fraud be detected. Repair Cost Waivers and OED Though for equity reasons it may be difficult for states to eliminate the waiver option for OED-tested vehicles, EPA recommends that states consider at least modifying waiver

23 Refer to SAEJl979 MODE 01PID00. 24 Refer to SAE J 1979 Section 4.2.4 Header Bytes. 19

### requirements for such vehicles. The reason for wanting to avoid granting a waiver to a vehicle with an illuminated MIL is two-fold: 1) it reinforces bad behavior (i.e., ignoring illuminated MILs) and 2) once lit, a MIL that was illuminated for a relatively minor problem effectively eclipses new, major problems, should they develop. At a minimum, the state's public education efforts regarding the OBD inspection should stress the importance of responding to illuminated MILs in a timely manner. Public Outreach In 

### recognition ofthe pivotal role repair technicians and the public play in the success ofl/M programs, EPA recommends that all states required to perform vehicle OBD system checks begin public outreach and technician training six months to a year prior to the beginning ofmandatory OBD testing25 • 

### Therefore, another reason for issuing this guidance at this time is to give states the opportunity to consider the various issues raised by and addressed in this guidance in the development oftheir public outreach and technician training efforts. The need for public outreach is also one ofthe reasons EPA has provided states several options for postponing the deadline for mandatory OBD testing beyond January 1, 2001 as part ofits April 5, 2001 rulemaking. To facilitate a smooth incorporation ofOBD-based testing ofOED-equipped vehicles into l/M programs states should not underestimate the importance ofeffective public outreach campaigns to inform motorists and the repair community about OBD and how it works, what the MIL is and how to respond to it, and the environmental and consumer benefits ofOBD. Thorough explanation ofthe OBD system within the context ofI/M testing may guard against the negative public perception which accompanied the introduction of loaded mode testing in many areas. Extra care may need to be taken in areas where loaded mode testing made the state emissions testing a "hot button" issue. Once developed, public educational materials should be disseminated as widely as possible. Relevant distribution points include: Trade organizations, dealerships (service writers as well as technicians), AAA and other insurance-provider newsletters, private garages, owners manuals for MY 1996 and newer vehicles, EPA publications, auto shows, drive-time radio advertisements, automotive magazines, and environmental public service announcements. In 

### pursuing their public outreach efforts, states should be sure to involve all relevant parties in the process ofdeveloping and distributing materials. These include: State

25 EPA also recommends that states consider factoring in a month or more ofvoluntary, advisory-only testing to allow inspectors and motorists to get accustomed to the program and to allow for debugging prior to the beginning ofmandatory testing with mandatory repairs upon failure. Under such a scenario, a vehicle would be given a complete OBD-1/M test with the exception that vehicles would not be failed on the basis ofthe OBD-1/M check alone, and would, instead, be issued an advisory notice indicating that the vehicle is experiencing a problem for which it will be failed ifcorrective action is not taken prior to the next test cycle. Under the one-test-cycle phase-in option allowed by the April 5, 2001 FRM, vehicles which fail the OBD-1/M check but pass the tailpipe inspection should be provided an advisory such as the one described above ifthey are excused from being repaired during the phase-in period. 

### 20

### legislators, local leaders, automobile manufacturers, automobile enthusiasts, scan tool manufacturers, EPA regional offices, emission inspection contractors, environmentalists, health professionals, AAA and other automotive insurance providers, technical colleges, service writers, private garages and repair chains. Technician Training The success ofa state's OED-I/M effort will also depend on making sure that the repair community is prepared to address the sorts ofvehicles that are identified by the OED scan as needing service and/or repair. States should work with their local educational institutions, OED equipment vendors, and other training providers to ensure that the necessary training is available to repair technicians in the field well in advance ofmandatory OED-I/M testing. In 

### addition, states should also work with the various organizations representing the repair community to stress the need for repair technicians to take advantage ofthe training opportunities that are available. In 

### I/M programs where repair technicians are licensed or certified by the state to participate in the program, OED-specific repair technician training should be required as a prerequisite to such licensing or certification. Such training should address the following topics, at a minimum: • The basics ofOED (i.e., theory, terminology, legal requirements, etc.) • The differences between OED I and OED II • The OED-I/M inspection procedure • The pass, fail, and rejection criteria for OED-equipped vehicles • Readiness, the setting and clearing ofcodes, and MIL-triggering vs. pending DTCs • The link between the OED-I/M check and the environment, and • Proper diagnostic procedures and available sources ofdiagnostic materials (i.e., manufacturers, hotlines, web sites, etc.).

21

### APPENDIX A Glossary of 1/M- and ORD-Related Terms Basic I/M: A vehicle inspection and maintenance program designed to meet the basic I/M performance standard which includes performance ofan idle test on 1968+ passenger cars. Under the 1990 Amendments to the Clean Air Act, basic I/Mis required in moderate nonattainment areas, as well as those areas already implementing or required to implement a basic I/M program prior to passage ofthe 1990 Amendments. "Check Engine" Light: See the definition for Malfunction Indicator Light (MIL) below. Diagnostic Trouble Codes CDTCs): An alphanumeric code which is set in a vehicle's onboard computer when a monitor detects a condition likely to lead to (or has already produced) a component or system failure, or otherwise contribute to exceeding emissions standards by 1.5 times the certification standard. Enhanced l/M: A vehicle inspection and maintenance program designed to meet one ofthree enhanced l/M performance standards - high, low, and ozone transport region (OTR) low. The high enhanced standard is designed around IM240 tailpipe testing and purge and pressure evaporative system testing. The low enhanced standard is similar to the basic l/M performance standard, but includes light-duty trucks and a visual antitampering inspection. The OTR low enhanced performance standard is designed for areas which would not be required to do I/M at all, save for their location within the Northeast Ozone Transport Region. The OTR low enhanced standard is based upon tailpipe testing using remote sensing devices and visual antitampering inspections. Serious and worse nonattainment areas are required to implement enhanced I/M, as well as all areas within the OTR with populations over 100,000, regardless ofattainment status. Evaporative System Test: A test ofa vehicle's evaporative control system to determine ifthe system is 1) leaking and/or 2) purging properly. Malfunction Indicator Light (MIL): Also known as a Check Engine light, the Malfunction Indicator Light ofMIL is illuminated on the dashboard when conditions exist likely to result in emissions exceeding standards by 1.5 times or worse. Alternatives include "Service Engine Soon," as well as an unlabeled picture ofan engine. Onboard Diagnostics COBO): A system ofvehicle component and condition monitors controlled by a central, onboard computer running software designed to signal the motorist when conditions exist which could lead to a vehicle's exceeding its emission standards by 1.5 times the standard. OBD Data Link Connector (DLC): The interface - usually located under the dashboard on the driver's side - between a vehicle's OBD computer and the OBD scanner. Connecting an

### OBD scanner to the DLC allows 

### VM inspectors and vehicle repair technicians to read the readiness status ofthe vehicle's various onboard monitors as well as any diagnostic trouble codes (DTCs). Readiness Code: A status flag stored by a vehicle's onboard computer which is different from a DTC in that it does not indicate a vehicle fault, but rather whether or not a given monitor has been run (i.e., whether or not the component or system in question has been checked to determine ifit is functioning properly) . Scanner or Scan Tool: A PC-based or handheld device used to interface with a vehicle's onboard computer for the purpose ofreading DTCs and monitor readiness status. Test-and-Repair: An 

### VM program which allows the same people who test a vehicle to also repair the same vehicle and retest it to determine whether or not the repairs performed were adequate. Test-and-repair programs are also generally decentralized, though not all decentralized programs are necessarily test-and-repair. Test-Only: An I/M program - usually, though not exclusively centralized - which requires that the functions oftesting and repair be performed by different, financially unrelated parties.

### APPENDIXB

Data Link Connector Mapping DiagramI I I I 

# Diagnostic Link Connector Mapping Diagram DriverSide

I I / I f

\ I ' 

# #7

I I I /_ 

### - 

## - - -

I 

# l Pref erred Connector Location

I I I I I I \ \ \ \ 

## PassengerSide

• I I I



# -- - '' 

# - - ---.-..

## __ ...... 

### ' \

........ '":;.. ...._, \ \ ..,_..._I



# ''·

) I / I

-- _.,,"" I 

## --=:::.... --.z:-.::::=____**~**



## ------------· --· 

# t-Vehicle Centerline

### Diagnostic Link Connector (DLC) Mapping Diagram Explanation The mapping diagram ofDLC locations contains a divided instrument panel (IP) with numbered areas. Each numbered area represents specific sections ofthe IP where manufacturers may have located DLCs . This document briefly clarifies the numbered locations on the mapping diagram. Areas 1-3 fall within the preferred DLC location while the remaining areas, 4-8, fall into the allowable DLC location according to EPA requirements. Areas 4-8 require that manufacturers label the vehicle in the preferred location to notify parties ofthe alternate connector location. 

### Preferred Location(s) Location #1: This location represents a DLC positioned on the underside ofthe IP directly under the steering column (or approximately 150mm left or right ofthe steering column) . Visualizing the underside ofan IP divided into three equal parts from inside the passenger compartment, this represents the center section. Location #2 This location represents a DLC positioned on the underside ofthe IP between the steering column and the driver' s side passenger door. Visualizing the underside ofan IP divided into three equal parts from inside the passenger compartment, this represents the left section. Location #3 This location represents a DLC positioned on the underside ofthe IP between the steering column and the center console. Visualizing the underside ofan IP divided into three equal parts from inside the passenger compartment, this represents the right section. 

### Allowable Location(s) Location #4 This location represents a DLC positioned on the upper part ofthe IP between the steering column and the center console (but not on the center console, see location #6). Location #5 This location represents a DLC positioned on the upper part ofthe IP between the steering column and the driver side, passenger door. Location #6 This location represents a DLC positioned on the vertical section ofthe center console and left ofthe vehicle center line. Location #7

### This location represents a DLC positioned 300 mm right ofthe vehicle centerline either on the vertical section ofthe center console or on the passenger side ofthe vehicle. Location #8 

### This location represents a DLC positioned on the horizontal section ofthe center console either left or right ofthe vehicle center line. This does not include the horizontal section of the center console that extends into the rear passenger area (see location #9) . Location #9 

### This location, not shown, represents any DLC positioned in an area other than those mentioned above (e.g., in the rear passenger area on the driver side armrest) .

### APPENDIXC

Vehicles with Hard-to-Find Data Link Connector Locations*, by 

### Make and Model Year (*Location numbers refer to DLC map in 

### Appendix B)Sheet1 Manufacturer I Year Model LocaUon/ 

## iComments 

### ! 

## I I Access I Audi 1996, 1997 Cabriolet, A6 9/cover rear ashtray ; Bentley 1996-2000 au 9/cover in glove box BMW 1999-2000 3 Series 2/cover 1/4 tum slot head screw BMW 1996-1998 3 Series (including '96·'99 M3) 2/cover 1 /4 tum slot head screw BMW 1996-2000 

### s Series 2/cover 1 /4 tum slot head screw - · BMW 1996. 2000**7-seri~** 6/cover under stero cntr1 

### ---· BMW 1996-2000 X3/M Roadsi;;,r 7/cover passenger side of c;onsole ' BMW 1996- 2000 Z3-series 9/cover underpassgr.dash Ferrari 1996-2000 all 3/open up high under the dash board Ford 1996 Bronco 7/cover Ford 1996 F Series 7/cover Ford 1996, 1997 Thunderbird/Cougar 7/cover Honda 1996- 1997 Accord 6/cover behind ashtray Honda 1997-1998 AcuraCL 7/open underpassgr. dash Honda 1999 Acura CL 8/open bove shifter Honda 1999-2000 Acura AL 8/cover In front of shifter behind ashtray Honda 1996-1998 AcuraTL · 8/cover behind ashtray . Honda 1999-2000 Acura TL 6/cover below radio next to seat heater control Honda 1997-2000 CR·V 7/open under P8SSOr. dash Honda 1996-2000 DelSol/Hvbrid 7/open under passgr. dash Honda 1996-1999 lntegra 7/open under passgr. dash Honda 1997-2000 NSX, S2,000 7/open under passgr. dash Honda 1996- 1998 Odyssey 7/cover console under passgr. dash Honda 1997- 2000 Prelude 7/cover under passgr. dash Honda 1996 Prelude 8/open above shifter Honda 1996-1998 Acura AL 7/open passenger side center console front Hyundai 1996-1998 Accent 2/open In coin box Lexus 1996 ES300 2/cover behind fuse box panel Lexus 1996-2000 LS400 2/cover above parking brake Lotus 1997- 2000 Esprit 7/open Above Passenger Dash Mazda 1998-1999 Mlata 2/cover behind fuse box panel Mitsubnhi 1996 Expo 2/open behind fuse box Porsche 1996 Ail Vehicles 6/cover driver's side of console Rolls· Royce 1996-2000 all 9/cover in glove box Rover 1997 Defender 6/cover under parcel tray Rover 1996- 2000 Range Rover 7/open under passngr dash Subaru 1996-2000 LeQacy 2/cover behind plastic hinged cover Subaru 1996-1997 

### svx 1/cover right side of steering column Toyota 1996 Avalon 2/cover behind fuse box panel Toyota 1996 Camry 2/cover behind coin box Tovota 2000 New Hvbrid 7/open Toyota 1996 - 1997 Prevla .(2/4 WO) 6/cover top lnstrumt panel Toyota 1996-1998 Tercel 2/cover behind fuse box panel Volvo 1997-1998 850 8/cover in front of shifter under coin tray VOLVO 1998- 1999 all vehicles except Sao 9/cover hand brake area Volvo 2000 C/SN70 8/cover Volvo 2000 SN40 6/cover 

## vw 1996-1998 Cabrio, GoH, Jetta 7/cover right side of ashtray 

## vw 1996-1999 Eurovan 4/cover on dash behind wiper lever 

## vw 1999 Golf,Jetta 7/cover 

### vw 1996 - 1997 Passat 4/cover on dash behind wiper lever Page 1

### APPENDIXD Manufacturers Known to Have OBD Readiness Issues 1996 Chrysler vehicles - Vehicles may clear readiness at key-off. Vehicles should be tested normally. Ifvehicles are found to be "Not Ready," they should be referred to a qualified service provider so the OBD software can be updated. 1996 - 1998 Mitsubishi vehicles -These vehicles may have a high degree of"Not Ready" for catalyst monitor due to a "trip based" design. Mitsubishi has provided driving cycles in its service information to allow monitors to operate. These vehicles should be scanned for MIL illumination without regard to readiness status. 1996 Nissan vehicles and 1997 Nissan 2.0 liter 200SX - These vehicles may have a high degree of"Not Ready"for catalyst and evaporative monitors due to a "trip based" design. Nissan has provided driving cycles in its service information to allow monitors to operate. These vehicles should be treated as other non-problematic vehicles. Nissan Technical Service Bulletin #NTB98-018, February 18, 1998. 1996-98 Saab vehicles - These vehicles may have a high degree of "Not Ready"for catalyst and evaporative monitors due to a "trip based" design. Saab has provided driving cycles in its service information to allow monitors to operate. These vehicles should be treated as other non-problematic vehicles. Saab Technical Service Bulletin not yet available. 1996 Subaru vehicles - Vehicles will clear readiness at key-off. There is no reprogramming available for this line ofvehicles. These vehicles should be scanned for MIL illumination without regard to readiness status. Subaru Technical Service Bulletin #11 -49-97R (see Appendix F ofthis guidance). 1997 Toyota Tercel and Paseo - Vehicles will never clear the evaporative monitor to "Ready." At this time no fix is available. Vehicles should be scanned using remaining readiness monitors as described for non-problematic vehicles. 1996 Volvo 850 Turbo - Vehicles will clear readiness at key-off. There is no reprogramming available for this line ofvehicles. These vehicles should be scanned for MIL illumination without regard to readiness status. Volvo Technical Service Bulletin #SB 2-23-0056. 1996-98 Volvo vehicles (excluding 850 Turbo) - These vehicles may have a high degree of "Not Ready"for catalyst and evaporative monitors due to a "trip based" design. Volvo has provided driving cycles in its service information to allow monitors to operate. These vehicles should be treated as other non-problematic vehicles. Volvo Technical Service Bulletin #SB 2-23-0056.

### APPENDIXE

OBD-1/M Test Procedure Flow ChartOBD l/M RECOMMENDED TEST PROCEDURE FOR 1996 MODEL YEAR AND NEWER VEHICLES .

Vehicle fails test (Note #1) 

### Start OBD l/M Test 

### Procedure

Center for Automotive Science and Tech nology Weber State Un iversity No Turn ignition switch to the "Off" position for at least 12 seconds

Locate DLC , connect test equipment Note MIL (MIL Illumination maybe brief) while turning ignition switch to the 

### "Run" position with**~ngine** "Off''

Start and leave engine running and establish communication with on-board system



### AOBD l/M RECOMMENDED TEST PROCEDURE FOR 1996 MODEL YEAR AND NEWER VEHICLES (Cont) Connect functional 

### approved test

equipment

Vehicle fails test 

### (Note #2)

Vehicle fails test (Note #4)



### B

Center for Automotive Science and Technology Weber State University No



### End

Yes Yes

No

Yes Yes

No

Vehicle fails test (Note #3)

BOBD l/M RECOMMENDED TEST PROCEDURE FOR 1996 MODEL YEAR AND NEWER VEHICLES

Retrieve DTCs using

Mode $03 request. Provide DTC's with

description on a Vehicle Inspection Report for repair and fleet failure characterization 

### Vehicle fails 

### OBD

l/M test

End View Readiness Code status (Data collection only)

Center for Automotive Science and Technology Weber State University 

### B

No

Vehicle is not ready

for l/M ·evaluation. Vehicle needs to be operated in such a way as to exercise all monitors. (Note #5) 

# c

Yes



### Vehicle passes 080 l/M test (Cont)

## Notes on flow chart: Note 1: The purpose of this step is to verify the On-Board Diagnostic (OBD) system has control of the Malfunction lnc:licator Light (MIL) and the MIL is functional. Operation of the MIL varies between vehicle manufacturers. Key On Engine Off (KOEO) typically results in the MIL on steady, however, there are systems which will illuminate the MIL only briefly during KOEO. In either situation MIL presence and illumination capability has been established. If the vehicle fails the l/M test at this point, the vehicle inspection report should indicate the MIL problem should be repaired and also include information gathered during the remaining 1/M test steps. 

### Note 2: It is important for the l/M testing personnel to verify proper diagnostic equipment operation before failing the vehicle . If the diagnostic equipment is functional then the vehicle's communication problem must be resolved. Without communication between the OBD system and the test equipment the 1/M test must be ended and the problem resolved before further interrogation of the vehicle can be performed . This step includes identification of Data Link Connector (DLC) tampering, serial data circuit problems and any other condition that would prevent the 08D system from communicating with the test equipment. · 

### Note 3: l/M test failure is a result of MIL illumination even though the OBD system has not commanded the MIL on, or has stored any Diagnostic Trouble Codes (DTCs); e.g., a serial data line failure between the OBD computer and the Instrument Panel. 

### Note 4: l/M test failure is a result of both the actual and commanded state of the MIL. DTCs should be stored since the MIL is commanded on. A vehicle 

### should not fail an l/M test when DTCs are stored but there is no MIL on; e.g., the OTC was stored by a loose gas cap which was subsequently tightened. 

### Note 5: Readiness Code status must be identified at this stage in the l/M test to determine whether or not all emission control systems have been tested by the 08D system. If any one (or more) Readiness Code(s) are not set ("ready'') the 08D system has not yet completed testing of the system(s) and failures may be present but not yet identified. It is important to understand that the vehicle 

### does not fail the l/M test at this point; no emission related faults have been identified. The current state of the vehicle's emission control system is 

### undetermined. The emission control systems and related components are tested under specific vehicle operating conditions. Therefore, to set the Readiness Codes the vehicle must be operated within these specific conditions (commonly referred to as "enable criteria") for the OBD system tests to be performed. Once testing of an emission control system is complete, the related Readiness Code will be set ("ready"). When all Readiness Codes are set, the vehicle is ready for further l/M testing. It will be at the states discretion whether to recommend the customer drive the vehicle to set the Readin. ess Codes or to take the vehicle for service. The state may also choose to use a dynamometer drive cycle.

### Note 6: EPA has revised the current readiness code requirement to allow states to complete the testing process on model year 1996 thru 2000 vehicles with two or fewer unset readiness codes; for model year 2001 and newer vehicles , the testing process could still be complete provided there is no more than one unset readiness code. It is important to understand that the vehicle does not fail the l/M test because an unset readiness code is not itself an indication of an emission problem with the vehicle .