United States

Environmental Protection

Agency

Air and Radiation EPA420-R-00-018

October 2000

Effectiveness of OBD II

Evaporative Emission

Monitors - 30 Vehicle

Study

 Printed on Recycled Paper

(Revised October 2000)
EPA420-R-00-018

October 2000

Effectiveness of OBD II Evaporative

Emission Monitors - 30 Vehicle Study

(Revised October 2000)

Martin Reineman

Transportation and Regional Programs Division

Office of Transportation and Air Quality

U.S. Environmental Protection Agency

NOTICE

This technical report does not necessarily represent final EPA decisions or positions.

It is intended to present technical analysis of issues using data that are currently available.

The purpose in the release of such reports is to facilitate the exchange of

technical information and to inform the public of technical developments which

may form the basis for a final EPA decision, position, or regulatory action.
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Note: This report is a revision of the August 2000 EPA technical report of the same title. The

earlier report had the appearance of a draft report, and therefore this report has revised line

spacing and page breaks. It also incorporates the results of a September 2000 FTP

evaporative emission test conducted at the Ford Motor Company, Allen Park, Michigan testing

laboratories. That result is discussed under “Ford Vehicle No. 192", in Section VII - Discussion,

and also in the Appendix, under the section “Ford Vehicles 155 and 192.”

I. Summary:

From April 1999 through May 2000, EPA conducted a study to evaluate the effectiveness of

onboard diagnostics (OBD II) evaporative emission monitors on a sample of in-use light duty

vehicles and light duty trucks. The purpose of the study was to determine if OBD II technology

is an effective and efficient means of identifying in-use vehicles with excess evaporative

emissions. The results of this study have been routinely shared at quarterly I/M OBD workgroup

meetings coordinated through the Mobile Sources Technical Review Subcommittee (MSTRS),

authorized under the auspices of the Clean Air Act Advisory Committee.

Based on the results from a 30 vehicle test program conducted under contract with Automotive

Testing Laboratories Inc. (ATL) in Mesa, Arizona, EPA has observed the following with respect

to the effectiveness of OBD II evaporative emission monitors on 1996-2000 model year

vehicles.

1) 22 of 25 OBD II evaporative emission monitors registered diagnostic trouble codes

(DTCs) when failure conditions were induced. The 22 vehicles which registered DTCs

showed no fault codes when the induced failure conditions were removed and the DTCs

cleared. In general, these observations suggest OBD II evaporative emissions monitors

work satisfactorily. 

Three of the vehicles with induced failures equal to or greater than 0.040 inch leaks did

not illuminate the MIL or register diagnostic trouble codes. Two of the three vehicles

were investigated in Ann Arbor using vehicles of identical make, model, and model year
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and found to perform correctly. Results from the third vehicle are still being examined.

2) Five vehicles tested with small leaks (less than 0.020 in. diameter) were analyzed

separately. Three of five vehicles calibrated to meet the 0.040 inch OBD leak standard

but tested with a 0.020 inch leak produced a diagnostic trouble code and illuminated the

malfunction indicator light (MIL). This suggests that some OBD systems are quite

robust and have leak detection capability well below the minimum requirement.

3) Three vehicles with induced leaks produced Federal Test Procedure (FTP)

evaporative emissions less than half the levels of the enhanced evaporative emission

standards, suggesting that “maintenance” problems are being identified by OBD even

though they result in emission levels below FTP standards.

4) Based on the effectiveness of OBD II evaporative emission monitors observed in this

study and their advantages (non-intrusive, very time efficient) versus functional I/M

evaporative emission pressure and purge tests, I/M OBD checks are a suitable

alternative to functional I/M checks on 1996 and later model year vehicles which use

evaporative emission monitors.

5) The induced failure results from vehicles built for compliance with Onboard Refueling

Vapor Control (ORVR) standards averaged approximately half the running loss and half

the hot soak plus diurnal levels compared to vehicles designed to meet only the

enhanced evaporative standards.

6) This study suggests enhanced and ORVR evaporative emission control systems are

durable and low emitting relative to the FTP enhanced evaporative emission standards.

7) Four vehicles showed post repair emission results which exceeded FTP emission

standards. Reasons for this were investigated on three of the four vehicles and they are

presented in the Discussion section of the report. The “high” emissions on the fourth

vehicle were only slightly above standards on the diurnal loss test and because this test

vehicle could not be retained for further testing, no explanation for the high emissions
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will be provided in this study.

II. Background:

Due to its positive potential and EPA’s awareness of difficulties with implementing effective I/M

functional evaporative I/M emission tests, EPA has devoted considerable resources to

understanding and assessing the viability of the OBD II system for detecting emission failures in

in-use vehicles. An EPA draft technical report “Evaluation of OBD for Use In Detecting High

Emitting Vehicles,” by Gardetto and Trimble, dated August 2000, presents data and analysis to

conclude that OBD II exhaust monitors function properly and are a technology that may be used

to replace functional exhaust emission tests for 1996 and newer model year vehicles. [1] This

30 vehicle study presents EPA’s findings regarding the effectiveness of OBD II evaporative

emissions monitors in detecting emission problems on a sample of light duty vehicles and

trucks. The report is based on results of a test program conducted for EPA under contract with

Automotive Testing Laboratories Inc. in Mesa, Arizona from April 1999 to May 2000. [2]

This study did not examine the issue of OBD evaporative emission readiness under in-use

driving conditions. This issue has been, and continues to be, addressed by EPA, in particular,

by analysis of OBD pilot test results from the Wisconsin I/M program on a vehicle/model year

specific basis. The incidence of OBD II vehicles with evaporative emission monitors which are

not ready at the time of an I/M test is discussed in an EPA technical report, “Analyses of the

OBD II Data from the Wisconsin I/M Lanes,” by Trimble. [3]

III. Objectives of the ATL Study:

The ATL laboratory study had four objectives:

1) Verify the operation of the evaporative emission monitors in a cross section of in-use

OBD II vehicles under laboratory test conditions.
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2) Measure evaporative emissions from vehicles with evaporative emission DTCs by

running the EPA Federal Test Procedure for vehicles designed to meet enhanced

evaporative emission standards.

3) Measure evaporative emissions from vehicles which have been repaired to remove

the DTCs on the same vehicles.

4) Based on the results of the first three objectives, determine whether OBD II is an

adequate surrogate for the functional I/M “pressure” and “purge” tests which were

originally recommended as part of the high enhanced I/M requirements.

IV. Test Protocol

Induced Failure Modes

Based on EPA’s inspection of evaporative emission DTCs and their causes, it was suspected

that the majority of evaporative emission failures in OBD vehicles can be attributed to loose gas

caps, but EPA does not, at present, have a source of published data to verify this assertion. 

Rather, it is based on undocumented experience gained during recruitment of OBD II vehicles

for test programs at the EPA National Vehicle Fuels and Emission Laboratory (NVFEL) and

discussions with I/M and OBD experts from domestic vehicle manufacturers. Rather than

recruit only loose gas cap vehicles as the primary source of “failed” vehicles, it was decided to

procure rental vehicles and induce a variety of failure modes which could occur in the OBD II inuse fleet. Inducing failures was thought to be necessary given that evaporative emission

failures are more age than mileage related, and we did not expect to find a variety of real world

failure modes.

Table A-1 in the Appendix describes the test fleet, and Table A-2 describes the induced faults,

the resulting DTCs, the drive cycles required to satisfy the readiness criteria for both “failure”

and “repair” sequences, and a comment column for more detail on specific vehicle test issues. 

Although only one set of drive cycles are listed in Table A-2, both induced failure and postrepair sequences used the same drive cycles to satisfy readiness criteria and exercise the OBD
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system. The induced failures in the 30 vehicle sample included the following:

Missing gas caps (3)

Loosening gas caps (2)

0.040 inch diameter leaks in gas caps or vapor vent lines (11)

Disabling canister fresh air inlet (1)

Disconnecting purge lines (8)

0.020 inch leaks in gas caps (5)

Each vehicle received only one induced failure condition. These failure modes are not meant to

represent the variety of real world failure modes, nor are they necessarily representative of the

range of excess emissions which results from real failures. Rather, they were selected because

they are reproducible, they are simple to repair, they are failure modes which a properly

functioning evaporative emission control system should detect, and vehicles with these induced

failures could be used to estimate the relation between the occurrence of an evaporative

emissions DTC and mass measurements of evaporative emissions on the same vehicle.

Induced Leak Size

Under California and Federal OBD requirements, vehicles equipped with OBD II evaporative

emission monitors for 1996-1999 model years are required to detect leaks of a hole size of

0.040 inches diameter or larger, and detect and identify a malfunctioning purge system. 

Beginning in the 2000 model year and phased-in nationwide through the 2002 model year, the

0.040 inch diameter leak check requirement becomes more stringent, requiring identification of

a 0.020 inch diameter leak. Five vehicles were tested with 0.020 inch diameter leaks to

examine the robustness of the current systems, and obtain estimates of the evaporative

emissions from vehicles which might pass the current OBD II leak check but have leaks that

may produce emissions above the current FTP standards.

Gas caps with 0.040 or 0.020 inch diameter leaks were supplied by Stant Manufacturing Corp.

and were built with flow tested, precision machined, square edged orifices. Previous EPA

attempts to produce such small leaks have shown that machining small orifices is not

straightforward. Flow calibration was provided with the orifices used in the gas caps and
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therefore EPA is confident the 0.040 and 0.020 inch diameter leaks in the test gas caps are

accurate.

The presence of induced failures of the evaporative emission systems were verified with

functional “pressure” and “purge” tests. These tests were conducted by measuring pressure

loss and purge system vacuum through the service port access on OBD evaporative emission

vehicles. Vehicles not equipped with the service port received pre-OBD functional tests. These

consisted of measuring pressure loss by pressurizing from the fill-pipe and monitoring the loss

of pressure versus time. Purge system failures were verified by using a roto-meter to check for

no purge flow. The “pressure” and “purge” tests conducted on vehicles without the service port

were performed by experienced ATL laboratory technicians.

The qualification that the tests were performed by experienced ATL technicians is an important

one because the U.S. vehicle manufacturers have been opposed to EPA’s pre-OBD intrusive

functional purge test, and to a lesser degree, the functional pressure test applied at the fuel

inlet. This study took care to avoid adversely influencing the evaporative emission results by

carefully conducting functional evaporative checks on vehicles not equipped with a service port

access.

Test Procedures

Following inspection for acceptable driveability, braking, and a leak free exhaust system, the

OBD system was checked for readiness status and the presence of DTCs or an illuminated

MIL.

Each vehicle’s OBD computer was reset to clear codes and show a “not ready” status prior to

FTP testing with an induced failure. Vehicles were typically operated on chassis dynamometers

to set a DTC and illuminate the MIL prior to the initial FTP exhaust and evaporative emission

test. Exception to this practice occurred only when a chassis dynamometer was not available,

at which time readiness criteria were satisfied by operating the vehicle over a local surface

street route which approximated the speed time relation of the LA-4 driving schedule. (The LA4, also known as the Urban Dynamometer Driving Schedule (UDDS) is the first 1372 seconds

of the FTP speed/time driving schedule used for sampling exhaust emissions. Vehicle operated

over the LA-4 typically satisfy enabling criteria and exercise the OBD evaporative emissions
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monitors.) Following the tests with the induced failures, each vehicle was repaired by the ATL

technicians. The OBD system was again reset to clear the fault code and set the readiness

status to a “not ready” state. The vehicle was then driven to satisfy readiness criteria and

determine if the OBD system correctly showed no DTC code and no illuminated MIL.

The FTP evaporative emission test selected for this study was the three day diurnal procedure

with running loss test. An abbreviated flowchart of the test procedure for the FTP evaporative

test is presented in Figure A-1 in the Appendix. In general, tests were conducted in accordance

with Title 40, Code of Federal Regulations (CFR) Part 86, Subpart B, revised July 1, 1998. [4] 

Gasoline meeting FTP fuel specifications was used for all exhaust and evaporative emission

tests. Fuel tank temperature profiles used for the running loss test are the profiles submitted to

EPA during the vehicle certification process. 

Deviations from Subpart B test requirements included: 1) using external surface mounted fuel

tank thermocouples (on vehicles with steel fuel tanks) as a surrogate for installing internal

thermocouples, 2) draining the fuel tank by using the vehicle fuel pump instead of installing a

fuel drain(s) at the lowest point in the fuel tank, and 3) permitting minor deviation from the

requirement that measured and target liquid fuel temperature agreement be within 3 degrees F

during the running loss test, 4) use of the EPA I/M Lookup Table for selecting the chassis

dynamometer inertia and horsepower for the 1996-1998 vehicles. (Test parameters for the

1999 and 2000 model year vehicles were obtained from EPA new vehicle certification data.)

Use of external mounted thermocouples instead of installing internal thermocouples is a

common EPA practice in in-use evaporative emission testing. Without this simplification,

instrumenting the vehicle in strict accordance with the EPA certification requirements for

locating thermocouples and fuel drains can require cutting access panels in the vehicle. ATL’s

past practical experience in using surface mounted thermocouples is that this location does not

compromise testing accuracy. Vehicles with plastic fuel tanks used thermocouples installed

through the bottom of the fuel tank. Any fuel tank modification that compromised the integrity

of the OEM tank was resolved by replacing the fuel tank before the vehicle was returned to the

owner.

The FTP evaporative emission running loss test requires that the measured fuel tank
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temperature track the target temperature within 3 degrees F over the dynamometer driving

portion of the running loss test (a series of four driving schedules in the order: one Urban

Dynamometer Driving Schedule, two New York City Cycles, a second Urban Dynamometer

Driving Schedule). In general, the measured fuel tank temperatures denoted as “Actual F”

(induced failure test) or “Actual R” (post-repair test) in Table A-5 in the Appendix indicate close

agreement with the vehicle manufacturer supplied fuel tank temperature profile. Manufacturer

supplied fuel tank target temperatures and ATL measured temperatures for starting and ending

segments of the running loss test are summarized in Table A-5 in the Appendix.

Exceptions to meeting the 3 degree tolerance were observed for vehicles 150, 154, 184, and

189. The deviations for these vehicles range from slightly over 3 degrees F to about 7 degrees

F. These deviations from the target temperature profile, and the short time of the excursion, as

a matter of engineering judgement are not thought to be important because their effect on

running loss results is judged to be insignificant.

V. Test Fleet

Vehicle Selection

The test vehicle descriptive information is displayed in Table A-1 of the Appendix. These data

include vehicle make, model, model year, mileage, engine family, evaporative emission family,

whether the vehicle was designed to comply with enhanced evaporative emission standards or

ORVR requirements, and chassis dynamometer test parameters. 

The test fleet is characterized as follows:

8 vehicle manufacturers - Ford (7), GM (7), Honda (3), Isuzu (1), Mazda (2), Mitsubishi

(1). Nissan (4), Toyota (5)

5 model years - 1996 (2), 1997 (1), 1998 (9), 1999 (16), 2000 (2)

Mileage range - 5,259 to 116,730
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20 light duty vehicles; 10 light duty trucks and SUVs

14 enhanced evap systems; 16 onboard refueling vapor recovery systems (ORVR)

29 rental vehicles; 1 privately owned vehicle

Inspection of the fleet shows the following: the sample is not sales weighted among

manufacturers or car versus truck sales, most vehicles are low mileage, and Chrysler vehicles

are not represented because they used an alternative Federal OBD certification provision in

effect for 1996-1999 model year vehicles, and therefore did not use OBD evaporative emission

monitors in their Federal certified vehicles. Because a sales weighted sample was not required

for this study, flexibility was permitted in obtaining vehicles. Nevertheless, the sample

described above represents the major vehicle manufactures and, where multiple vehicles were

sampled from a manufacturer, the sample reflects an “approximate” sales ranking.

VI. Results

Complete evaporative emission results from the 30 vehicles are presented in Table A-3 in the

Appendix. Note in Table A-3, that the letters E or R appended to the ATL identification number

designate whether the vehicle is designed to comply with the enhanced evaporative emission

standards, or the enhanced plus on-board refueling vapor recovery standards, respectively. 

These design standards classifications were determined by decoding the evaporative emission

family name which is located on the underside of the vehicle’s hood.

DTC and MIL illumination status resulting from the induced failures were separated into two

samples and summarized as follows:

DTC Response and MIL Illumination from Induced Failures on 25 Vehicles

(9 Purge system failures, 16 leaks 0.040 in. diameter)

 DTC Set: 22 MIL Illuminated: Same 22
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DTC Response and MIL Illumination from Induced Failures on 5 Vehicles

(5 gas caps with leaks of 0.020 in.)

 DTC Set: 3 MIL Illuminated: Same 3

The five vehicles with induced leaks of 0.020 inches were not included in the 25 vehicle stratum

in order to not “penalize” vehicles for finding leaks more stringent than their OBD design

requirements.

An analysis of the purge failure results in Table A-3 shows that specific DTCs registered for

similar induced failures were inconsistent among vehicle manufacturers for faults induced in the

purge control systems of eight vehicles. Vehicle manufacturers’ proposals are under

consideration which would lead to more standardization among DTCs.

Emission results are summarized below in the tables below, stratified as a function of

evaporative emission control design - enhanced evap or ORVR designs, and divided between

the induced failure results (Failures) and the post-repair results (Repairs). 11 vehicles were

certified to the enhanced evap standard and 11 were designed to comply with ORVR

requirements. Tables 1 and 2 divide the evaporative emission results into these strata because

the design of ORVR systems (larger canisters, larger vapor lines, other unique components to

control refueling loss) may also lead to lower evaporative emission loss. ORVR designs are

manufacturer and vehicle design specific, and although their exact ability to produce inherently

low evaporative emissions with the failure modes used in this study was not investigated, the

data in Table 2 suggest lower evaporative emissions from ORVR control systems when

compared to enhanced control systems (Table 1).

Table 1

Means (x) and Standard Deviations (s) 11 Enhanced Evaporative Emission Vehicles

Failures Repairs

Running Loss, g/mi x = 7.86 x = 0.02

s = 7.89 s = 0.01

1 hr Hot Soak Loss, g x = 10.74 x = 0.13
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s = 16.12 s = 0.08

High 24 hr Diurnal Loss, g x = 20.83 x = 0.95 (N=10)

s = 17.77 s = 0.87

Table 2

Means (x) and Standard Deviations (s) for 11 ORVR Evaporative Emission Vehicles

Failures Repairs

Running Loss, g/mi x = 4.51 x = 0.02

s = 5.29 s = 0.01

1 hr Hot Soak Loss, g x = 2.89 x = 0.14

s = 3.20 s = 0.07

High 24 hr Diurnal Loss, g x = 12.31 x = 0.87

s = 12.00 s = 0.51

Not all vehicles had “fail” and “repair” pairs because not all of the vehicles registered DTCs, and

not all vehicles had valid “repair” results. Therefore, Table 2 presents results from only 22 of

the 30 vehicles. Repaired results which were not deemed to be valid are described in the

Discussion section of this report.

21 of 22 after repair tests produced running loss emissions less than the enhanced running loss

standard of 0.05 g/mi. Although the induced failures were simplistic and easy to rectify, the low

running loss emissions after repairs show that this test sample of in-use vehicles is quite clean,

i.e. below FTP standards. 

20 of 21 after repair results showed hot soak plus diurnal (high 24 hour result) emissions less

than the enhanced evaporative emission standard of 2.0 g. This also shows that this sample of
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in-use vehicles is low emitting with respect to FTP evaporative emission standards.

The results summarized in Table 3 are the means of the combined repair effects (11 enhanced

vehicles plus 11 ORVR vehicles) in Tables 1 and 2.

Table 3

Means (x) and Standard Deviations (s) of Repair Effects (Failure - Repair) for 22 Vehicles

Running Loss, g/mi x = 6.17 s = 6.78

1 hr. Hot Soak Loss, g x = 6.68 s = 12.04

High 24 hr Diurnal Loss, g x = 14.18 (N=21) s = 14.54

The repair effects for 22 evaporative emission repairs were substantial: 6.2 g/mi for the running

loss test, 6.7 g for the hot soak test, and 14.2 g for the high 24 hr result for the diurnal loss test

(21 vehicles). The range among the evaporative emission test results for the induced failures is

large, as evidenced by values of the standard deviation which are equal to or greater than the

mean. Emission results of the repaired vehicles did not exhibit the scatter observed by the

“failed” vehicles.

Composite and bag by bag FTP exhaust emission results are summarized in Tables A-3 and A4, respectively, in the Appendix.

Based on the results presented in Tables 1-3 above, and follow-up emission testing at ATL on

one vehicle, and on two vehicles at the EPA NVFEL, EPA concludes that, in general, OBD II

evaporative emission monitors accurately identify vehicles with evaporative emission problems,

and the repair effects observed by comparing pre and post repair FTP emission levels are

substantial. These findings satisfy the first three of four objectives of this study.

EPA believes the fourth objective, determining if using an OBD II scan tool to check MIL and

DTC status is an acceptable I/M test for identifying in-use evaporative emission failures, has
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also been satisfied. This is based on the observations that 1) vehicles with illuminated MILs

and evaporative emission DTCs have high emissions when compared against FTP evaporative

emission standards, 2) the OBD scan for evaporative emissions is accurate and unintrusive,

unlike pre-OBD II I/M functional evaporative emission “pressure” and “purge” checks, which are

often impractical due to the inability to access the evaporative emission system, and/or risk of

damage to the vehicle, and 3) using a scan tool in an I/M environment is very time efficient,

requiring only about 30 seconds to conduct an entire OBD check once the scan tool is inserted

in the data link connector, versus several minutes for functional tests.

VII. Discussion

OBD and I/M Gas Cap Tests

Reference [5] contains data that suggest the incidence of gas cap failures on 1998 model year

OBD vehicles, determined using a functional leak test on the gas cap, is over 30 times the

incidence of evaporative emission failures detected by the OBD monitor. Although this study

did not quantify evaporative emissions from real world gas cap leaks, it would be desirable to

collect such data in the future. Nevertheless, there appears to be an adequate benefit from

conducting a stand alone functional gas cap test as part of the OBD check of the evaporative

emission system. This is based on examining the emission results from the two vehicles with

0.020 in. diameter leaks in gas caps which were not identified by the OBD system. Even

though the OBD systems in these two vehicles were not designed to find 0.020 in. leaks, EPA

believes the mass emissions from leaking gas caps which are below the 0.020 in. threshold

may still be significant over the in-use operation of the vehicle. Therefore, at present and until

more data are available, EPA is recommending conducting a standard I/M gas cap check in

conjunction with a scan of the OBD II system.

OBD II and I/M Pressure/Purge Tests

This study did not directly compare the effectiveness of OBD II evaporative emission monitors

to the functional I/M pressure and purge tests proposed by EPA in the 1992 I/M rule. The

reasons for this were twofold. 
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First, the failure criteria for functional I/M pressure and purge tests differ from the criteria used

by OBD II vehicles, and therefore it would require a considerably larger sample than 30 vehicles

to prove if there are differences between numbers of failures found by either method (identified

independently by either method), and analyze the possible mass emissions reductions which

could result from repairing vehicles identified by OBD II vs. functional testing. Pre-OBD II I/M

pressure tests fail vehicles which lose more than six inches of water column pressure in two

minutes starting from an initial pressure of six inches of water above ambient pressure. A

vehicle fails the I/M purge test if the system flows less than 1.0 liters of a hydrocarbon and air

mixture when measured at a point between the evaporative emission canister and the engine

intake. The OBD II criteria require identifying vehicles with leaks in the vapor space of an

equivalent hole size of at least 0.040 in. diameter (0.020 in. diameter leak identification is being

phased-in nationwide for light duty vehicles starting with the 2000 model year). OBD II criteria

for identifying defective purge systems require that a test be conducted to determine the

presence of purge flow, such as an actual flow measurement, or indirect indicators of purge

flow such as monitoring changes in air fuel ratio, to prove the canister is being purged. The

OBD checks are performed whenever the vehicle is operated and enabling criteria have been

satisfied. OBD II requirements for identifying malfunctioning evaporative emission systems

were developed by the California Air Resources Board in the early 1990's independent of the

EPA I/M 1992 functional pressure and purge tests.

More detailed discussions of the theoretical relationship between the OBD II 0.040 inch

detection requirement and the pre-OBD functional pressure check, including estimating the

merits of running a functional pressure test on OBD II vehicles with no MIL illuminated or no

DTC, are contained in references [6] and [7]. Based largely on discussions among members of

the MSTRS OBD workgroup, it is likely that the number of small leaks undetected by OBD II

would be low, repairing such vehicles may be difficult, and conducting dual testing on OBD

vehicles would be inconsistent with the data collected from this study.

Second, since the 1996 model year, and including some 1995 model year vehicles, vehicles

have been designed to meet the enhanced evaporative emission standards. This standard

resulted in the usage of less permeable and more durable materials, such as hard vapor lines

between the fuel and tank and the canister which are not capable of being clamped without

damage, and use of connectors which either could not be easily removed after vehicle
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assembly, or terminated in connections which prevented timely installation of hardware to

conduct a pressure or purge test. Since the 1998 model year, manufacturers have produced

vehicles designed to the FTP ORVR requirements. In general, vehicles without service ports

can no longer receive a functional pressure test from the fillpipe location due to the presence of

components to prevent liquid fuel spitback and vapor loss during refueling. Although the

number of OBD II vehicles with evaporative emission monitors but without service ports is not

easily documented, EPA estimates it constitutes a significant number of the OBD II vehicles

equipped with evaporative emission monitors. 

From EPA observations and discussions with vehicle manufacturers, only OBD II vehicles which

are equipped with the evaporative emission “service port” are capable of conducting a

functional I/M pressure or purge test. In an I/M environment this would most safely and

efficiently require a bi-directional scan tool which can also be used for directly reading the MIL

status and DTCs. Therefore it appears that the service port is best used in the vehicle service

industry to diagnose evaporative emission failures and confirm repairs.

Some I/M stakeholders have been concerned about not having the capability of testing an OBD

vehicle which has a “not ready” status at the time of the I/M OBD check. In order to alleviate

this concern, the MSTRS workgroup issued a consensus position stating it is acceptable to

conduct an I/M leak check of the evaporative emission system on OBD II vehicles using the

service port, or a method approved by vehicle manufacturers, if such functional tests are

determined to be cost effective for the specific I/M program. [8] EPA will issue separate

guidance on this and other implementation issues in the near future.

ATL Vehicles which had Difficulty Illuminating MILs and/or High Post-Repair Evaporative

Emissions

Three vehicles, Nos. 150, 155, and 182, had difficulty illuminating MILs and registering DTCs

after faults were induced in the evaporative emission control system. Three other vehicles,

Nos. 153, 188, and 192, had high levels of running loss and/or hot soak plus diurnal emissions. 

This section summarizes the concerns with those vehicles, and where resolution of the issue(s)

was reached, this is also presented. A more detailed discussion of these six vehicles, including

references to relevant correspondence, is presented in the Appendix.
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Vehicles with Difficulty Illuminating MILs - Two Mazda vehicles, Nos. 150 and 182 (1998 Mazda

626s), and Ford vehicle No. 155, (1999 Mercury Tracer) had difficulty illuminating MIL lights and

setting DTCs during the period ATL had possession of the vehicles.

Vehicle Nos. 150 and 182 - The Mazda 626s had considerable difficulty illuminating MILs when

a gas cap was removed (Vehicle 150), and when tested with a gas cap with a 0.040 inch leak

(Vehicle 182). Vehicle 182 was specifically recruited to investigate the problems observed

earlier with vehicle 150. When ATL again had difficulty setting the MIL light and producing a

DTC, EPA asked for Mazda’s assistance to determine why vehicle 182 was not responding to

the induced failure condition.

After considerable investigation by Mazda and EPA technical staff, including two test programs

in Ann Arbor, MI, it was determined that the Mazda vehicles did respond correctly when missing

or leaking gas caps were installed and two similar Mazda 626s were driven on a chassis 

dynamometer and later driven on local road routes in the Ann Arbor area. However, during the

investigation it was determined that Mazda had neglected to list a change in engine load

enabling criterion. It appears that the 1998 Mazda 626 may be sensitive to an individual’s

driving behavior, and this affects the ability of the vehicle to exercise the evaporative emission

monitor. Ultimately, it was unknown why ATL’s experiences with the Mazda 626, in particular

vehicle 182, were different from EPA’s results in Ann Arbor.

Analysis of OBD data from the Wisconsin I/M program also verified that the 1998 Mazda 626

did not have an abnormal “not-ready” rate at the time the OBD system was examined as part of

the Wisconsin IM240 test.

Vehicle No. 155 - ATL was not able to set a MIL light on a 1999 Mercury Tracer when a leaking

gas cap was installed. After several attempts to set the MIL, EPA contacted Ford technical staff

and requested their assistance. Ford suggested the vehicle be driven over their steady state

driving cycle (unlike most OBD monitors which are designed to be run using cold start FTP

driving cycles, Ford requested and received approval from EPA to use an evaporative emission

monitor which functions when driven at steady state conditions) even though ATL did use

steady state driving when attempting to illuminate the MIL and set a DTC. Ford also requested

the tank be filled to 80% of capacity versus the standard 40% fuel fill for cold start FTP testing.
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The suggestions by Ford did not exercise the monitor and the vehicle had to be returned to the

rental agency because the initial phase of the 30 vehicle study ended. No resolution for the

difficulty with this vehicle was reached and EPA is continuing to examine the OBD evaporative

emission monitor on the 1999 Mercury Tracer and the Ford Escort.

Vehicles with High Post-Repair Evaporative Emissions

Three vehicles, Nos. 153, 188, and 192, had suspiciously high post-repair evaporative

emissions relative to either the FTP running loss standard and/or the FTP hot soak plus diurnal

loss standard. Given that the vehicles were relatively new and the “repairs” to the vehicles were

very straightforward and were not likely to be the source of high evaporative emissions,

considerable effort was expended in examining these three vehicles.

Honda Vehicle Nos. 153 and 188 - Vehicles 153 and 188 are 1999 Honda 2.3 liter Accords. A

number of actions were taken by ATL to examine the reasons for the running loss, and high hot

soak plus diurnal loss emissions for the post-repair test on vehicle 153. The first phase of the

ATL contract period expired before the emissions results could be explained, and therefore

vehicle 188 was recruited to further examine the results observed with vehicle 153.

When high evaporative emissions were again observed with vehicle 188 and ATL diagnostic

investigations did not find a cause for the results, EPA requested technical assistance from

Honda.

Honda staff made multiple visits to ATL to confirm the original post-repair results and also to

examine in detail a number of differences between ATL’s and Honda’s equipment and

procedures for instrumenting the fuel tank, and supplying heat to the fuel tank during the

running loss test. Honda collected test results in Japan by replicating the systems and

procedures used by ATL. Later, Honda returned to ATL and ran tests using procedures and

equipment similar to those used for Certification testing of the Accord in Japan. When using a

Honda-like system at ATL, running loss results were below FTP standards.

Honda concluded it was the combination of improper thermocouple placement in the fuel tank

and an ATL heating system which produced localized and excessive heating of the fuel tank

that lead to erroneously high evaporative emission results on vehicles 153 and 188.
-19-

EPA plans to investigate the test procedure issues in greater detail because both ATL and

Honda claim to be following the requirements in the CFR related to thermocouple placement

and heating system design and control.

Ford Vehicle No. 192 - Vehicle 192 is a 1998 3.8 liter Ford Windstar which produced hot soak

plus diurnal emissions above the 2.0 gram standard. Because ATL diagnosis of the vehicle and

test equipment did not produce an explanation for the high emission result, Ford technical staff

were invited to offer their assistance. Ford had a number of concerns regarding the ATL test

procedure and equipment, but no obvious engineering explanation was provided which would

suggest ATL’s results were erroneous.

Ford did not wish to visit ATL and more closely examine the vehicle, test equipment, and

procedures, but they did offer to supply a Windstar fuel tank to ATL which was instrumented in

a manner similar to a Certification test configuration. EPA decided not to conduct tests with the

tank offered by Ford because it would have required access panels be cut in the floor of the

vehicle to accommodate the protruding thermocouples and fuel drains which are typically used

in testing of Certification prototype vehicles. The vehicle was then released to the rental

agency because the second phase of the test program came to an end.

EPA asked if Ford would test a similar Windstar at their Allen Park, MI Certification facility, and

in September 2000 Ford submitted FTP evaporative emission results of 0.80 g (hot soak loss

plus highest 24 diurnal loss) and 0.003 g/mi (running loss). These results are well below the

FTP evaporative emission standards and, at present, EPA has no plans to conduct follow-up

testing to resolve the differences between results from ATL and Ford.

Although exact explanations for the high post-repair emissions were not provided for vehicles

153, 188, and 192 discussed above, explanations would likely be determined if more time and

resources were devoted to studying them. Of equal or greater concern is the possible

emissions sensitivity to differences in laboratories’ running loss equipment and test procedures. 

These issues require more attention.
-20-

VIII. Conclusions

1) In general, OBD II evaporative emission monitors operated properly on a 30 vehicle sample

of OBD II vehicles. This conclusion is based on the proper performance of the OBD system

when evaporative emission failures were induced, the absence of codes or illuminated MILs

when the failures were removed, and analysis of the FTP. 

2) Based on the observations above, and given the impracticality of using functional I/M (preOBD) purge and fillpipe pressure checks on OBD vehicles, OBD II evaporative emissions

checks are a suitable replacement for functional evaporative emission I/M tests. 

3) Based on data from the Wisconsin I/M program that show over 30 times as many OBD

vehicles fail the stand alone gas cap test as compared to setting an evaporative emission DTC,

EPA recommends that gas cap testing continue for OBD I/M checks.

4) The emissions data show, in general, OBD II vehicles with evaporative emission DTCs and

illuminated MILs exceed FTP evaporative emission standards, while vehicles without DTCs and

illuminated MILs are below FTP evaporative emission standards. The repair effects associated

with performing I/M evaporative tests using scan tools and OBD II technology, appears to be

substantial.

IX. Recommendations

The following recommendations are based on this study:

1) It is desirable to conduct emission tests on a larger sample of OBD II vehicles, including

vehicles designed to comply with the California Air Resources Board (CARB) 0.020 inch leak

check requirements. Future test programs should include more real world evaporative emission

failures and also include real world repairs.

2) Given the testing issues raised in analyses of the Mazda, Honda, and Ford vehicles, it would
-21-

be useful to conduct a study of the evaporative emission sensitivity to thermocouple location

and fuel tank heating system design.

X. Acknowledgments

Completion of this study would not have been possible without the assistance of the vehicle

manufacturers whose vehicles comprised the 30 vehicle sample: Ford, General Motors, Honda,

Isuzu, Mazda, Mitsubishi, Nissan, and Toyota. These manufacturers provided timely assistance

in locating fuel tank temperature profiles for the running loss test and also in addressing vehicle

specific testing issues.
-22-

XI. References

1. Gardetto, E, Trimble, T; “Evaluation of OBD for Use In Detecting High Emitting Vehicles,”

EPA Technical Report, August 2000

2. Data from EPA Work Assignments 3-12 and 0-4, SHED Tests on OBD II Evap Vehicles, EPA

Contract No. 68-C99-241 - Automotive Testing Laboratories; 1999-2000

3. Trimble, T; “Analyses of the OBD II Data from the Wisconsin I/M Lanes,” EPA Technical

Report, August 2000

4. Subpart B, Part 86, Protection of the Environment, Code of Federal Regulations, Revised

July 1, 1998

5. Data submitted to EPA from the Wisconsin I/M program for 1996-1999 model years, July

2000

6. Reineman, Martin; “EPA Position on Conducting Functional I/M Tests on OBD Vehicles”,

memo to FACA I/M OBD Sub-group Members, 7 April, 2000

7. Alliance of Automotive Manufacturers; “I & M Evaporative System Pressure Check and OBD

II Inspection,” 13 January, 2000

8. Reineman, Martin, and Mow, Vince; “Issue: Conducting Functional Pressure Tests on OBD

Vehicles,” Position statement presented to FACA OBD I/M Workgroup, 19 April, 2000

9. Reineman, Martin, Regional and State Programs Division; “Tests with Mazda 626s”, EPA

memo to Arvon Mitcham, Vehicle Programs and Compliance Division, 9 November, 1999

(Business Confidential)
-23-

10. Mitcham, Arvon, “1998 Mazda 626 Evaporative Monitor Road Evaluation”, EPA report,

November, 1999 (Business Confidential)

11. Motohashi, Masa, Mazda North American Operations; “Summary of Mazda/EPA OBD II

Road Test”, report submitted to Arvon Mitcham, Vehicle Program and Compliance Division, 17

November, 1999 (Business Confidential)

12. Raney, David; Cover Letter and Report, “Test and Research Report - Investigation of High

Evaporative Emissions from 1999 Accord at ATL” Ref. No. AHPRO-E00008, submitted to

Martin Reineman, EPA, July 27, 2000

13. Reineman, Martin; personal conversations with Harry Diegel, Principal Engineer, Vehicle

Environmental Engineering, Surveillance and Compliance Dept, Ford Motor Company, 2 June,

2000

14. Diegel, Harry; test results submitted to Martin Reineman, Regional and State Programs

Division.
-24-

Appendix
-25-

Selected Results from Individual Vehicles

Mazda Vehicles 150 and 182 - Vehicles 150 and 182 are 1998 Mazda 626s with identical

engine and evaporative emissions families. In Table A-2, results from vehicle 150 with a

missing gas cap show that three cold start LA-4s, two cold start FTPs, one cold start five minute

45 mph steady state, and one hot start 20 minute 60 mph steady state cycle were run in an

attempt to set the evaporative emission monitor to “ready”, set a DTC, and illuminate a MIL. All

cold starts were preceded by an overnight soak at 75 F. Following the last steady state cycle,

the MIL was still not illuminated but a code 0455 (large leak) was recorded in the continuous

memory of the OBD system. The vehicle was then FTP tested. Following installation of the

gas cap, two cold start LA-4s, two cold start steady states, and one cold start FTP were run to

set the evaporative emission monitor to “ready” and observe the MIL and DTC status. At the

end of this sequence the evaporative emission monitor was still not ready but the vehicle was

FTP tested in its “repaired” state.

Because vehicle 150 did not illuminate a MIL or produce a DTC, EPA contacted technical staff

at Mazda and began to jointly investigate whether there was a design problem with the OBD

evaporative emission monitor, or there were test protocol or vehicle instrumentation issues

which might explain the apparent problems with the OBD system. Meetings were held among

Mazda and EPA technical staff members, and a series of dynamometer and road tests were

conducted in Ann Arbor, MI on two 1998 Mazda 626s identical to vehicle 150. EPA also

analyzed data from the Wisconsin IM240 program to determine if 1998 Mazda 626s had high

incidences of being “not ready” at the time of the I/M test. The results of these investigations

and analyses are summarized in references [9], [10], and [11].

Reference [9] describes the results of a test program run on chassis dynamometers at the EPA

NVFEL. One vehicle was instrumented to record a series of real time engine and evaporative

emission control parameters. These parameters were recorded by using a custom powertrain

control module (PCM) and Mazda’s auxiliary on-board data recording system. Discussions with

Mazda and inspection of the identification numbers on the PCM confirmed the custom PCM
-26-

was identical to the production unit with the exception of its ability to output parameters to an

on-board data collection system. One vehicle was tested with a missing gas cap and the other

vehicle was tested with a gas cap with a 0.040 in. diameter leak. Results from reference [9]

show the OBD evaporative emission monitors performed properly by illuminating MILs and

setting DTCs on the second cold LA-4 driven with each vehicle.

Reference [10] describes a test program conducted at the EPA NVFEL which evaluated the

ability of the evaporative emission monitor to detect a missing gas cap when the same vehicles

used for the dynamometer study were driven over a series of road routes in the Ann Arbor area. 

This study showed that when the two vehicles were driven over a variety of road routes with

several different drivers, MILs and DTCs were observed on 6 of 13 road trials. Reference [10]

also describes the result of an analysis of data from the Wisconsin I/M test program. A check

of the readiness status at the time of the Wisconsin I/M test on 152 Mazda 626s during the

period August, 1998 through July, 1999 showed a “not ready” condition for only four vehicles. 

The analysis did not examine the reason for the not ready status, but even if the evaporative

emission monitor was the reason for all four vehicles being “not ready”, this is not judged to be

a significant concern. Based on the dynamometer and road test programs at the NVFEL, and

an analysis of the Wisconsin data, EPA concluded the Mazda 626 OBD evaporative emission

monitors operated acceptably.

Reference [11] is an engineering report submitted by Mazda describing the need for an

additional enabling criterion. This report requests a “change in load < 4.0/sec” enabling

criterion be added to their 1998 model year OBD application description. This criterion is based

on the change in load fraction, expressed as a decimal from 0 to 1.0 during a period of 50

msec. The load fraction is based on the ratio of measured engine air flow divided by the air

flow at a maximum load condition, and thus the numerator is dimensionless. The enabling

criterion specifies that the rate of change in engine load must be less than a certain value. The

enabling criterion added by Mazda implies that a driver should operate the vehicle in a “smooth

manner” to obtain more frequent operation of the evaporative emission monitor.

During the period when the EPA was investigating the two Mazdas in Ann Arbor, ATL began

testing a second Mazda 626. Vehicle 182 experienced difficulty in setting codes and

illuminating MILs when tested with a 0.040 in. diameter leak in the gas cap, and also had high
-27-

evaporative emissions in its “repaired” FTP test. The test history with vehicle 182 can be

observed by examining the Fault, MIL, Code, Drive Cycle to Set Code, and Comments columns

in Table A-2, and the emission results in Table A-3. Table A-3 uses the labels F1, R1, F2, and

R2 to designate the first series of “failed” and “repaired” FTP tests, and the second series of

“failed” and “repaired” tests, respectively. The identifier “Diag” refers to a diagnostic test which

was performed to investigate reasons for the high evaporative emissions.

Note in Table A-2 that vehicles 182, 183, and 184 used several road driving cycles while

attempting to illuminate MILs or produce DTCs. This occurred because ATL was installing a

dynamometer in their laboratory and construction limited the access to and usage of their other

dynamometers.

No MIL or DTC were present following two cold start LA-4s when vehicle 182 was driven on a

road route with a 0.040 in. diameter leak in the gas cap. When the fault was removed and the

FTP repeated, the running loss emissions were high. The cause for the high evaporative

emissions was investigated and attributed to an inaccurate measurement of the fuel

temperature which caused the fuel to be heated excessively, thereby generating high quantities

of hydrocarbon vapor during the running loss test. The emission results in Table A-3

designated as “Diag” shows that correcting the over heating condition by using internal fuel tank

thermocouples lowered the running loss emissions below the 0.05 g/mi standard.

Given that the previous emission tests, F1 and R1 were now suspect, the vehicle was rerun

with a 0.040 gas cap leak. No MIL or DTCs were observed after the second cold start even

though the evaporative emission monitor status was “ready.” A second FTP test was run with

the leaking gas cap, and these are reported as F2 in Table A-3. A second FTP test was run

with the fault removed and these results are reported as R2 in Table A-3. The gas cap was

then removed and two cold LA-4s were run on the dynamometer. The MIL illuminated and 

DTC 0455 (large leak) was registered. One more attempt was made to illuminate a MIL and set

a DTC with a 0.040 in. leak in the gas cap by running a series of cold start LA-4s, but after the

third LA-4, no MIL was illuminated and no DTC was observed.

There are no obvious reasons for the apparent differences in MIL illumination and DTC

response between the ATL and Ann Arbor investigations. EPA suspects the evaporative
-28-

emission monitor in the 1998 Mazda 626 may not be easy to exercise during transient driving,

although EPA reported more success in Ann Arbor in illuminating MILs and registering DTCs

with induced faults. Neither of the Mazda vehicles tested at ATL were judged to have

accurately identified a 0.040 inch leak, and therefore they constitute two or the three vehicles

which did not illuminate MILs or register DTCs. Similarly, because they did not illuminate MILs,

these vehicles did not qualify for inclusion in Tables 1- 3, which required that they illuminated

MILs, set DTCs, and did not have questions concerning the validity of the evaporative emission

results presented in Table A-3, particularly the post-repair tests.

Vehicles with High Post-Repair Evaporative Emissions

Two Honda vehicles, Nos. 153 and 188, had high evaporative emission results for the post

repair FTP tests. Two Ford vehicles, Nos. 155 and 194, also had high evaporative emissions

for the post repair FTP tests.

Honda Vehicles 153 and 188 - Vehicle 153 is a 1999 Honda Accord LX with a 2.3 liter engine. 

This vehicle produced high evaporative emissions during the running loss, and subsequently in

the hot soak and diurnal portions of the FTP. The fault induced in vehicle 153 was a

disconnected purge line which was blocked at the end of the disconnection and also at the

connection on the purge valve. Given the simplistic failure mode, there appears little likelihood

that the vehicle was not restored to its original configuration for the “repaired” mode test. Unlike

the problems described above for the Mazda vehicles, the OBD system had no difficulty in

illuminating the MIL and setting a DTC.

A number of actions were taken by ATL to investigate the causes of the apparent high

evaporative emissions first observed during the second bag of the first LA-4 cycle of the

running loss driving schedule. They included checking for leaks, checking the adsorption

efficiency of the canister by purging, loading, and weighing the canister, checking for adequate

purge volume by installing a flowmeter, probing for sources of hydrocarbon vapor while driving

a series of three LA-4s with the vehicle on a chassis dynamometer, probing for vapor sources

when the vehicle was placed in the SHED after the series of LA-4s, and checking the

performance of a two way control valve in the vapor control system. No cause for the high

evaporative emissions was found and the vehicle had to be returned to the rental agency when

the contract period expired at the end of September, 1999.
-29-

The contract work with ATL was begun again in October, 1999. Given the unexplained

difficulties with vehicle 153, another 1999 Honda Accord, vehicle 188, was recruited for the

study. 188 was identical to vehicle 153 but used a 0.040 in. diameter leak in the gas cap as the

induced failure condition. Again, post-repair FTP results showed high levels of evaporative

emissions starting with the fourth bag (2nd NYCC) during the running loss test. The hot soak

and diurnal loss results were also high compared to the 2.0 g FTP evaporative emission

standard.

A second set of tests with and without the induced fault were run, this time using thermocouples

located in the fuel liquid, as opposed to the earlier test which attached thermocouples to the

exterior fuel tank surface. These tests are identified as F2 and R2, respectively, in Table A-3. 

Although each FTP test sequence suggested lower running loss emissions (significantly lower

for the repaired tests, 6.43 g/mi vs. 0.66 g/mi), the “repaired” test results still exceeded FTP

standards. Analysis of the data showed hydrocarbon breakthrough occurred at the end of the

sixth bag (second bag of the second LA-4) of the running loss driving schedule. 

Honda conducted an extensive effort to find a cause for the high evaporative emissions

reported during the post-repair FTP tests of vehicle 188. [12] Honda staff reviewed the second

by second temperature versus time profile during the running loss tests of vehicle 188, and

visited ATL to examine differences in test equipment between ATL and their certification test

facility in Japan.

On April 4 and 5, Honda witnessed a running loss test that confirmed the previously reported

high emissions. This series of tests used certification conditions for the dynamometer inertia

and road load horsepower. These values were higher than the previous load settings, 3375 vs.

3250 pounds, and 7.8 vs. 5.2 horsepower. The running loss result, 0.38 g/mi was lower than

earlier results, but still much higher than the 0.05 g/mi. standard. During the visit to ATL,

Honda speculated that the location of the thermocouples in the fuel tank and the design and

position of the ATL fuel tank heating system may have lead to localized tank heating and

therefore higher evaporative emissions.

Honda conducted a baseline running loss test at their certification facility Japan on a similar

Accord. This test produced a running loss result of 0.022 g/mi, well under the 0.05 g/mi
-30-

standard. Next, they located thermocouples in positions similar to those used by ATL in their

initial tests, and also duplicated the design of the ATL fuel tank heating system at their

certification test facility in Japan. A running loss result of 0.031 g/mi was obtained following

these modifications. Honda noted that their “simulated ATL system” did not control liquid or

vapor temperature to within the CFR requirements, but given the higher vapor and liquid

temperatures relative to the certification target profiles, Honda stated the evaporative emission

control system was designed with a significant margin of safety.

Honda stated that the thermocouple positions used by ATL to monitor the interior fuel

temperature were not in strict accordance with the CFR requirement for a “mid-volume” position

at a 40% fill level of nominal tank capacity. [4]

A second series of FTP tests were conducted at ATL on May 15 and 16 using a tank heating

system designed to approximate the system used for certification testing in Japan. These tests

also used a Honda supplied fuel tank with internal thermocouples located at the positions used

by Honda in their certification tests. The outlet area of the new air supply was slightly larger

than the outlet area of the standard ATL system (approximately 187 in2 vs. 157 in2 ) and the

modified system at ATL simulated the supply duct in Japan with respect to its location under the

fuel tank. The outlet area of the modified system was restricted to achieve an adequate supply

velocity. This was one of several design compromises which were made at ATL because the

air flowrate was higher in Japan with similar duct sizes. Reference [12] includes photographs

which show the original and modified systems at ATL and in Japan.

The net effect of the modifications to the ATL heating system and use of a fuel tank with

different positions for the thermocouples was to produce FTP running loss below the FTP

standard, 0.019 g/mi, and low hot soak emissions. Honda concluded it was the combination of

improper thermocouple placement and a heating system which produced localized and

excessive heating of the fuel tank which produced the erroneously high evaporative emission

results on vehicles 153 and 188.

EPA desires to conduct follow-up testing on these vehicles to quantify the localized heating

condition and the sensitivity to thermocouple placement on running losses, as the standard

system used by ATL has been successfully used on many different vehicle/fuel tank
-31-

combinations without adversely affecting a vehicle’s evaporative emission results. It is

important to note that both Honda’s and ATL’s running loss fuel tank equipment meet the CFR

requirements.

Ford Vehicles 155 and 192 - Vehicle 155 is a 1999 model year Mercury Tracer with 2.0 liter

engine. The Ford OBD evaporative emission monitor operates under steady state conditions

unlike most evaporative emission monitors which are designed to operate on cold LA-4 and/or

cold start FTP driving cycles. A gas cap with a 0.040 in. leak was installed and combinations of

LA-4s and steady state cycles were run to illuminate a MIL and set a DTC. A cold LA-4

followed by a cold steady state did not illuminate the MIL. The OBD system was reset, and a

cold LA-4, cold start steady state, and hot start LA-4 sequence did not illuminate the MIL,

although the evaporative emission monitor had completed its leak check. The FTP test was

then run with the leaking gas cap followed by the post-repair FTP.

Ford engineering staff were notified of the test results. They requested the leaking gas cap be

re-installed, the fuel tank filled to 80% capacity, and a cold LA-4, cold steady state, and second

cold steady state driving cycle be run. The MIL was still not illuminated after this sequence of

drive cycles, and the vehicle had to be returned to the rental agency because the initial portion

of the ATL contract period had expired.

Vehicle 192 is a 1998 Ford Windstar with a 3.8 liter engine. The induced failure was a 0.040 in.

diameter leak between the fuel tank and the canister. One cold start FTP and two cold start

steady state tests illuminated a MIL and produced a DTC. The vehicle received its initial FTP,

the fault was removed, and after readiness criteria were satisfied, the vehicle was retested on

the FTP. Running loss and hot soak emissions were low, but the vehicle showed high diurnal

emissions on each of the 24 hour portions of the three day diurnal test sequence. ATL

technicians inspected the vehicle for leaks, and although the initial leak check of the vehicle did

not indicate any leaks, inspection after the post-repair FTP emission test showed a possible

leak at the sending unit seal. The seal was replaced and the vehicle FTP tested again. These

results are identified as test R2 in Table A-3, and show the vehicle again exceeded the FTP hot

soak plus diurnal standard. The vehicle was again checked for leaks but none were found and

due to time constraints, the vehicle was returned to the rental agency.
-32-

EPA again contacted Ford technical staff and requested their assistance in determining why the

vehicle exhibited high levels of evaporative emissions during the diurnal test. Ford requested a

number of details concerning test equipment and test procedures used at ATL. Ford’s

concerns included the possibility that installation of the thermocouples through the bottom of

the tank may have induced trace leaks, the position of the thermocouples in the fuel may have

been incorrect, the diagnostic leak checks completed by ATL indicated inconsistent results, the

fuel tank heating system did not closely duplicate the heating system used by Ford during

certification testing of the 1998 Windstar, and the dynamometer inertia weight and 50 mph

actual horsepower were low compared to the certification test parameters.

Ford’s concerns are theoretically valid in that significant differences in instrumentation and test

parameters may influence evaporative emission results, but EPA did not prove that these

concerns, or combinations of them, were responsible for the high diurnal emissions measured

on either of the post-repair FTPs. 

The inertia and horsepower for the ATL tests on the 1998 Windstar were based on data from

the EPA I/M Look-up Table. Certification vehicles, based on engine family groupings, do not

accurately reflect the real world, “as built” fleet, which appear in I/M lanes. Real world vehicles

are aggregated in the look-up table differently than the methodology certification vehicles

(prototypes) use to represent multiple vehicles. For instance, a vehicle arriving for an I/M test

which appears to be uniquely identified in terms of manufacturer, model year, model name,

body style, number of cylinders, engine displacement, and transmission may have multiple

combinations of inertia weight and horsepower in the EPA certification records. The look-up

table is based on selecting the lowest inertia and/or dynamometer horsepower from EPA

certification records when multiple values are listed. Therefore, the lower vehicle inertia

selected at ATL, 3875 pounds versus 4250 pounds in the certification data, and the lower

horsepower, 7.9 versus 10.0, are not unexpected. Ford staff expressed the view that,

qualitatively, the lower dynamometer conditions would be expected to result in an incrementally

smaller quantity of purge flow during tests at ATL. It is unknown how this affected the diurnal

loss emissions at ATL.

Because no obvious reason for the high evaporative emissions could be determined, Ford

offered to send ATL a Windstar fuel tank instrumented in a manner identical to a fuel tank used
-33-

during the certification of the 1998 Windstar vehicle. It was determined that this would require

that access panels be cut in the floor of the vehicle to accommodate the protruding

thermocouples and fuel drains which are commonly present on certification vehicles. Given

that this vehicle was procured from a rental agency, this was unacceptable unless EPA or Ford

were to purchase the vehicle. Neither party wished to do this and the vehicle was returned to

the rental agency without a determination of a reason(s) for the high diurnal emissions.

EPA asked if Ford would consider running an evaporative emission test on a similar vehicle at

their Allen Park, Michigan certification test facility to demonstrate that, the ATL results

notwithstanding, the 1998 Windstar meets CFR requirements for FTP evaporative emissions. 

EPA staff met with Ford and were given a tour of the test equipment and protocols which Ford

used during the certification process for the 1998 Windstar. EPA asked, and Ford agreed, to

test a similar Windstar at their Allen Park, MI Certification facility. [13] 

In September 2000 Ford submitted FTP evaporative emission results of 0.80 g (hot soak loss

plus highest 24 diurnal loss) and 0.003 g/mi (running loss). [14] These results are well below

the FTP evaporative emission standards and, at present, EPA has no plans to conduct followup testing to resolve the reported emission differences between ATL and Ford.
Veh Model Disp Odom Tank Vol Tank Evap 

No. Yr Make Model liters miles Engine Family Evap Family gal Material Std 

140 99 Honda Civic 2.0 7,576 XHNXV01.6CA3 XHNXR0099AAD 16.0 Metal ORVR 141 96 Ford Explorer 4.0 116,730 TFM4.028GKFK TFM1120AYMED 21.0 Metal Enhance142 99 Chevrolet Tahoe 5.7 9,440 XGMXA05.7186 XGMXE0111911 30.0 Plastic Enhance143 98 Toyota Camry 2.2 21,197 WTYXV02.2XBA WTYXR0135AK1 18.5 Metal ORVR 144 99 Chevrolet Monte Carlo 3.1 7,978 XGMXV03.4041 XGMXE0095904 16.6 Metal Enhance145 98 Nissan Altima 2.4 35,574 WSNXV02.4A3A WNSXR0110RCA 15.8 Plastic ORVR 146 99 Mitsubishi Mirage 1.5 9,442 XMTXV01.5GFD XMTXR0140A1A 12.4 Metal ORVR 147 97 Ford Taurus 3.0 49,443 VFM3.0V8GKEK VFM1115AYMEB 16.0 Metal Enhance148 99 Toyota Pickup 2.4 78,042 XTYXT02.4BBH XTYXE0095AE0 15.1 Metal Enhance149 99 Chevrolet Cavalier 2.2 16,124 XGMXV02.2021 XGMXR0124912 15.0 Metal ORVR 150 98 Mazda 626 LX 2.0 21,378 WTKXV02.0VBA WTKXR0125BFA 16.9 Metal ORVR 151 98 Chevrolet Lumina 3.1 31,859 WGMXV03.1041 WGMXE0095904 16.6 Metal Enhance152 99 Ford Ranger 3.0 5,259 XFMXT03.32DC XFMXE0155FBE 19.5 Plastic Enhance153 99 Honda Accord LX 2.3 12,950 XHNXV02.3PA3 XHNXR0130AAA 17.1 Metal ORVR 154 99 Nissan Sentra 1.6 29,362 XNSXV01.6A1A XNSXR0085RCA 13.3 Metal ORVR 

Vehicle Descriptions

Table A-1
155 99 Mercury Tracer 2.0 12,782 XFMXV02.0VBA XFMXR0080BAE 12.8 Metal ORVR 

156 99 Toyota Sienna 3.0 30,611 XTYXT03.0XBP XTYXE0115AE1 21.0 Metal Enhance182 98 Mazda 626 2.0 32,854 WTKXV02.0VBA WTKXR0125BFA 16.9 Metal ORVR 183 00 Nissan Maxima 3.0 6,742 YNSZV03.0A6A YNSXR0110RCC 19.5 Metal ORVR 184 99 Mercury Gr.Marquis 4.6 25,678 XFMXV04.6VBE XFMXR0115BAE 19.0 Metal ORVR 185 98 Chevrolet S-10 4.3 14,745 WGMXT04.3183 WGMXE009504 18.5 Metal Enhance186 98 Ford F-150 4.6 73,787 WFMXT04.6BAA WFMXE0160BAE 24.5 Metal Enhance187 99 Infinity QX4 3.3 27,453 XNSXT03.3A5B XNSXE0110MBA 21.2 Metal Enhance188 99 Honda Accord 2.3 11,636 XHNXV02.3PA3 XHNXR0130AAA 17.2 Metal ORVR 189 00 Toyota Corolla 1.8 7,592 YTYXV01.8FFA YTYXR0115AK1 13.2 Metal ORVR 190 99 Toyota Tacoma 2.4 41,142 XTYXT02.4BBH XTYXE0095AE0 15.2 Metal Enhance191 96 Isuzu Rodeo 3.2 77,640 TSZ3.22JGKEK TSZ1089AYME0 21.9 Metal Enhance192 98 Ford Windstar 3.8 68,892 WFMXT03.8ABA WFMXE0140BBE 20.0 Plastic Enhance193 98 Chevrolet Malibu 3.1 29,871 WGMXV03.1041 WGMXR0124912 15.0 Metal ORVR 194 99 Pontiac Grand Am 2.4 21,666 XGMXV02.4024 XGMXR0124912 15.0 Metal ORVR 
Veh

No. Fault MIL Code Drive Cycles Comments

140 Removed the gas cap On P1456 LA-4 (1)140 Reinstall OEM Cap Off None141 Purge system inoperative On P1451 No drive cycle needed True failure.141 Replaced PCM Off None142 0.040 in. leak in gas cap On P0442 LA-4 (2)

142 Reinstall OEM cap Off None143 0.040 in. leak in vent line On P0440 LA-4 (2.5)143 Removed 0.040 in. leak Off None144 Blocked purge line On P0440 LA-4 (2) Removed purge line at throttle body, plu144 Blockage removed Off None145 Vent solenoid line to On P0450, LA-4 (2)

atmosphere blocked P1446

145 Blockage removed Off None146 0.040 in. leak in gas cap On P0442 LA-4 (2)146 Reinstall OEM cap Off None147 Purge and tank vent line On P0455 LA-4 (1) SS (1) Port disconnected from cansiter. Open 

disconnected at canister True failure.

147 Lines reconnected Off None148 0.040 in. leak in purge line On P0446 LA-4 (2) Leak in series between solenoid and fue

to fuel tank.

148 Remove leak Off None

Induced Failures, MIL and Diagnostic Trouble Code Status

Table A-2
149 Disconnect purge line at On P0440 LA-4 (2) Plugged at both ends.

throttle body

149 Reinstall purge line Off None150 Remove gas cap Off None LA-4 (6) FTP (2) SS(1)150 Remove gas cap Off None SS (2) Continuous code P0455, No MIL.151 0.020 in. leak in gas cap Off None LA-4 (3) FTP (1)151 Reinstall OEM cap Off None152 0.020 in. leak in gas cap Off None LA-4 (1) Steady State (2)152 Reinstall OEM cap Off None153 Block purge line On P1457 LA-4 (2.5) Line disconnected from purge valve, blo

at both ends.

153 Repair purge line Off None154 0.040 in. leak in purge line. On P1440 LA-4 (2) Leak between canister and purge valve154 Remove leak Off None155 0.040 in. leak in gas cap Off None All readiness monitors complete, no MIL155 Reinstall OEM cap Off None156 0.020 in.leak in gas cap On P0440 LA-4 (4) MIL on after 4th LA-4.156 Reinstall OEM cap Off None182 0.040 in.gas cap leak Off None Road LA-4 (2) EGR & evap monitors incomplete after 

all monitors complete after 2nd. No MILcodes, all TIDs and CIDs pass.

182 Reinstall OEM cap Off None Road LA-4 (2)182 0.040 in.gas cap leak Off None LA-4 (2) All monitors complete after 2nd LA-4.182 Gas cap removed On P0455 LA-4 (2) MIL on during 2nd LA-4.182 2nd 0.040 in.gas cap leak Off None LA-4 (3) Vehicle had continuous code P0442 afte

drive trace. No cont. codes after 3rd drreadiness monitors complete, MIL off.
183 0.040 in.leak in line between On P0440 Road LA-4 (2) MIL on during 2nd road LA-4.

canister and fuel tankLeak removed from line

183 Remove leak from line Off None LA-4 (1) All monitors complete after first dyno LA184 Gas cap removed On P0455 Road LA-4 (2) SS (3) Steady state cycles performed on dyno.184 Gas Cap Installed Off None LA-4 (1) SS (1) Steady state cycles performed on dyno.185 0.040 in. leak in line between Off None Road LA-4 (1) All monitors completed during the first r

canister and fuel tank No MIL on, no codes.

185 Fault removed Off None LA-4 (2) GM (1) EGR monitor was reset during GM trace185 Reinstall 0.040 leak (metal) On P0442 LA-4 (2) Steel adapter put in in place of plastic a

2nd As-Received test performed.

186 Purge hose plugged On P0455 LA-4 (2) SS (4) Continuous code P0455 after first drive 

MIL on 5 minutes into the 4th steady sta

186 Remove plug from purge lin

e Off None FTP (1) SS (1) Evap only incomplete monitor after FTP

187 Loose gas cap On P0440 FTP (1) LA-4 (4) All monitors complete, no

MIL after 1st LA-4. Monitors cleared, ca1/2 in. Cold FTP trace driven. All moniexcept evap after FTP trace. No continThree more LA-4 cycles driven. MIL on into the 3rd LA-4 trace. (1 FTP + 3 LA-4 MIL on).

187 Tighten OEM cap Off None FTP (2)188 0.040 in.gas cap leak On P1456 LA-4 (2) Light on 15 minutes into the 2nd LA-4 d188 Install OEM cap Off None FTP (1) All monitors complete after 1st dyno FT188 0.040 in.gas cap leak On P1456 FTP (2)188 OEM gas cap installed Off None FTP (1) All monitors complete.189 0.020 in.gas cap leak On P0440 FTP (2)189 OEM gas cap installed Off None FTP (1) All monitors complete.
190 Purge line disconnected at On P0446 FTP (2) Vehicle procured with MIL on and fault s

canister

190 Reconnect purge line Off None FTP (1)191 Loose gas cap On P0440 FTP (2) Evap monitor incomplete, no pending co

first FTP.

191 Tighten gas cap Off None FTP (1)192 0.040 in.leak between tank On P0442 FTP (1) SS (1)

and canister.

192 Remove fault Off None FTP (1) SS (1)193 Blocked purge system On P0440 FTP (2)193 Reconnect pur

ge Off None FTP (3)

194 0.020 in.leak in gas cap On P0440 FTP (3)194 Reinstall OEM cap Off None FTP (2)
Veh Failure/ Test Test Test SHED Test 

No. Repair No. HC CH4 CO NOx CO2 MPG No. Grams gr/mi No. Grams No. No. G

140R F 21060 0.03 0.03 0.6 0.04 273 32.4 21064 220.86 12.81 3057 3.91 15 3058 

R 21306 0.04 0.03 1.1 0.03 282 31.3 21256 0.28 0.02 3085 0.10 15 3087 

12.80 3.81 

141E F 21173 0.15 0.11 1.1 0.28 441 20.1 21175 289.62 16.75 3078 2.72 15 3079 

R 21246 0.14 0.10 1.8 0.49 504 17.5 21248 0.57 0.03 3093 0.25 12 3094 

16.72 2.47 

142E F 21571 0.10 0.09 1.7 0.26 618 14.3 21572 46.35 2.69 3097 8.62 15 3098 

R 21618 0.09 0.08 1.8 0.26 621 14.3 21620 0.31 0.02 3104 0.15 14 3105 

2.67 8.47 

143R F 21253 0.14 0.13 1.5 0.24 344 25.6 21255 118.34 6.88 3095 3.62 14 3096 

R 21613 0.13 0.12 1.6 0.17 329 26.8 21615 0.17 0.01 3102 0.09 15 3103 

6.87 3.53 

144E F 21589 0.12 0.11 1.3 0.10 411 21.5 21591 91.67 5.31 3099 54.88 14 3100 

R 21639 0.09 0.08 1.2 0.10 392 22.5 21641 0.24 0.01 3108 0.11 14 3109 

5.30 54.77 

145R F 21677 0.08 0.07 1.3 0.20 355 24.9 21679 78.87 4.57 3112 0.72 15 3113 

R 21743 0.07 0.06 1.4 0.24 347 25.5 21745 0.24 0.01 3123 0.12 12 3124 

4.56 0.60 

146R F 21663 0.15 0.13 1.7 0.19 297 29.7 21665 0.17 0.01 3110 0.07 15 3111 

R 21705 0.14 0.12 1.6 0.15 291 30.3 21707 0.18 0.01 3114 0.07 15 3115 

0.00 0.00 

147E F 21791 0.16 0.14 1.4 0.24 423 20.9 21726 375.91 21.84 3119 23.66 15 3120 

R1 21857 0.25 0.22 2.5 0.43 453 19.4 21859 77.03 4.49 3143 8.28 12 3144 R2 21970 0.20 0.18 1.8 0.29 420 21.0 21972 0.21 0.01 3177 0.07

21.83 23.59

148E F 21888 0.18 0.15 2.4 0.27 358 24.5 21890 1.55 0.09 3150 0.80 14 3151 

R 21993 0.18 0.15 2.1 0.30 363 24.2 21995 0.32 0.02 3183 0.13 11 3185 

0.07 0.67 

149R F 21913 0.07 0.05 1.9 0.04 360 24.5 21914 111.79 6.52 3155 8.96 15 3156 

R 22006 0.09 0.08 1.4 0.04 351 25.1 22008 0.34 0.02 3189 0.30 14 3192 

6.50 8.66 

Table A-3

Not P

Composite Emission Results

Composite Emissions, g/mi Running Loss Hot Soak 3 D
150R F 21996 0.14 0.12 1.2 0.23 362 24.4 21999 95.01 5.53 3184 2.76 14 3186 

R 22137 0.13 0.12 0.9 0.20 349 25.4 22140 0.49 0.03 3230 0.18 11 3232 

151E F 22023 0.15 0.13 2.4 0.13 380 23.1 22026 18.43 1.07 3196 0.98 11 3199 

R 22081 0.14 0.11 2.0 0.15 383 23.0 22083 0.20 0.01 3215 0.06 14 3217 

152E F 22013 0.10 0.09 1.6 0.05 490 18.0 22015 0.34 0.02 3193 0.10 12 3204 

R 22132 0.09 0.09 1.5 0.03 491 18.0 22134 0.13 0.01 3228 0.05 12 3229 

153R F 22072 0.07 0.06 2.2 0.06 343 25.7 22074 212.01 12.29 3210 4.02 12 3214 

R 22166 0.04 0.04 1.6 0.05 350 25.2 22141 164.24 9.51 3231 2.98 11 3239 

154R F 22086 0.10 0.08 2.5 0.07 300 29.3 22088 3.50 0.20 3216 0.14 12 3218 

R 22177 0.10 0.08 2.2 0.08 298 29.5 22179 0.39 0.02 3241 0.12 12 3242 

0.18 0.02 

155R F 22155 0.06 0.05 0.5 0.09 303 29.2 22157 0.28 0.02 3234 0.09 12 3238 

R 22202 0.07 0.07 0.7 0.08 305 29.0 22204 0.31 0.02 3249 0.14 12 3250 

156E F 22121 0.21 0.18 1.4 0.22 434 20.4 22123 45.16 2.62 3223 6.83 14 3226 

R 22182 0.16 0.14 1.3 0.17 390 22.7 22186 0.39 0.02 3244 0.08 15 3247 

2.60 6.75 

182R F1 22262 0.17 0.15 1.1 0.27 346 25.6 22264 128.00 7.42 3255 34.67 14 3256 

R1 22300 0.15 0.14 1.0 0.23 347 25.5 22302 86.43 5.02 3262 11.65 12 3263 

Diag 22456 0.14 0.13 1.2 0.24 353 25.0 22458 0.48 0.03

F2 22518 0.33 0.32 1.5 0.26 354 24.9 22520 46.40 2.69 3301 0.47 12 3301 

R2 22578 0.16 0.14 1.3 0.24 269 23.9 22557 0.44 0.03 3313 0.09 12 3314 

2.66 0.38 

183R F 22368 0.10 0.09 1.1 0.22 412 21.5 22370 16.57 0.96 3277 0.67 11 3278 

R 22438 0.09 0.08 0.9 0.20 412 21.5 22440 0.26 0.02 3288 0.11 12 3289 

0.94 0.56 

184R F 22398 0.33 0.25 6.1 0.06 462 18.8 22400 4.48 0.26 3281 0.55 11 3282 

R 22461 0.12 0.11 1.9 0.06 457 19.3 22463 1.11 0.06 3293 0.11 11 3294 

0.19 0.44 

185E F1 22414 0.16 0.13 1.6 0.25 491 18.0 22416 9.29 0.54 3283 0.12 12 3284 

F2 22571 0.15 0.13 1.6 0.26 499 17.7 22548 8.08 0.47 3310 1.72 12 3311 

R 22469 0.14 0.12 1.6 0.29 480 18.4 22471 0.43 0.03 3295 0.05 12 3296 

0.44 1.67 

186E F 22612 0.19 0.16 2.0 0.35 537 16.4 22614 262.43 15.14 3325 5.40 12 3326 

R 22679 0.18 0.15 1.8 0.37 542 16.3 22681 0.23 0.01 3343 0.04 11 3344 

Not Perf Not P
15.13 5.36 

187E F 22618 0.13 0.12 1.3 0.36 567 15.6 22620 272.47 15.75 3329 11.54 12 3357 

R 22712 0.13 0.12 1.3 0.39 586 15.1 22714 0.43 0.03 3355 0.12 12 3357 

15.75 11.42 

188R F1 22609 0.11 0.18 0.7 0.01 287 30.8 22611 215.72 12.55 3324 21.41 11 3324 

R1 22663 0.06 0.05 1.9 0.04 339 26.0 22635 111.31 6.43 3333 5.34 12 3335 

F2 22694 0.07 0.06 1.5 0.04 335 26.4 22696 191.01 11.05 3348 16.21 12 3351 

R2 22728 11.33 0.66 3365 2.77 11 3366 R3 0.02 0.14

189R F 22733 0.05 0.05 0.7 0.07 282 31.4 22735 42.22 2.44 3368 5.09 12 3370 

R 22763 0.06 0.05 0.5 0.08 285 31.1 22765 0.35 0.02 3388 0.13 12 3389 

2.42 4.96 

190E F 22859 0.20 0.17 3.1 0.18 381 23.0 22831 101.89 0.92 3417 0.92 12 3419 

R 22921 0.13 0.11 1.8 0.16 370 23.8 22923 0.38 0.02 3442 0.14 12 3443 

0.90 0.78 

191E F 22849 0.15 0.14 1.2 0.33 615 14.4 22851 84.87 4.90 3422 1.02 13 3424 

R 22873 0.15 0.13 1.3 0.33 612 14.5 22875 0.81 0.05 3430 0.28 12 3431 

4.86 0.74 

192E F 22860 0.10 0.10 1.1 0.16 467 19.0 22862 4.16 0.24 3427 0.33 13 3428 

R1 22931 0.10 0.09 1.0 0.12 457 19.4 22933 0.63 0.04 3445 0.27 13 3445 R2 22985 0.09 0.09 0.8 0.11 453 19.6 22969 0.68 0.04 3458 0.28 12 3458 

193R F 22940 0.14 0.12 1.6 0.12 380 23.2 22942 258.60 14.92 3446 7.63 12 3447 

R 23005 0.16 0.14 2.4 0.07 375 23.4 23007 0.45 0.03 3465 0.18 12 3466 

14.90 7.45 

194R F 22959 0.14 0.13 0.9 0.24 370 23.9 22961 1.39 0.08 3455 0.42 11 3456 

R 23032 0.10 0.09 1.1 0.18 383 23.1 23034 0.41 0.02 3470 0.22 12 3471 

Not PerformedNot Performed Not P
Veh Failure/

No. Test Repair THC NMHC CO NOx CO2 MPG THC NMHC CO NOx CO2 MPG THC NMHC 

140 20160 F 0.13 0.13 2.2 0.06 290 30.2 0.00 0.00 0.1 0.03 280 31.8 0.01 0.01 

21306 R 0.15 0.14 4.0 0.00 302 28.8 0.01 0.00 0.4 0.03 289 30.8 0.01 0.01 

141 21173 F 0.47 0.41 4.9 0.47 463 18.9 0.06 0.02 0.0 0.17 459 19.4 0.08 0.05 

21246 R 0.44 0.38 6.6 1.03 523 16.6 0.05 0.02 0.0 0.16 526 16.9 0.10 0.06 

142 21571 F 0.34 0.29 6.9 0.59 644 13.6 0.04 0.04 0.2 0.06 637 13.9 0.05 0.04 

21618 R 0.34 0.29 7.5 0.49 646 13.5 0.02 0.02 0.2 0.10 641 13.9 0.04 0.03 

143 21253 F 0.55 0.52 5.7 0.67 373 23.2 0.02 0.01 0.1 0.12 355 25.1 0.06 0.04 

21613 R 0.54 0.50 6.3 0.56 358 24.0 0.02 0.01 0.3 0.05 334 26.6 0.05 0.03 

144 21589 F 0.48 0.45 5.4 0.38 412 21.1 0.02 0.01 0.1 0.02 441 20.2 0.05 0.03 

21639 R 0.37 0.34 5.5 0.36 390 22.3 0.01 0.00 0.0 0.00 422 21.1 0.04 0.03 

145 21677 F 0.30 0.27 4.5 0.43 401 21.7 0.02 0.02 0.3 0.08 342 26.0 0.03 0.02 

21743 R 0.26 0.24 4.2 0.46 406 21.5 0.02 0.01 0.7 0.13 340 26.1 0.03 0.02 

146 21663 F 0.56 0.51 6.2 0.36 308 27.8 0.02 0.02 0.4 0.13 306 29.0 0.09 0.06 

21705 R 0.51 0.47 5.4 0.38 323 26.7 0.02 0.02 0.4 0.09 294 30.2 0.07 0.06 

147 21797 F 0.51 0.46 5.9 0.61 427 20.3 0.03 0.02 0.0 0.08 452 19.7 0.14 0.12 

21857 R 0.85 0.77 9.0 0.65 456 18.8 0.05 0.03 0.6 0.29 483 18.4 0.20 0.17 

148 21888 F 0.70 0.63 10.0 0.53 381 22.3 0.03 0.02 0.3 0.15 368 24.1 0.06 0.04 

21993 R 0.70 0.63 9.1 0.65 382 22.3 0.03 0.02 0.1 0.13 376 23.6 0.06 0.04 

149 21913 F 0.41 0.37 7.7 0.20 396 21.7 0.02 0.01 0.1 0.00 370 24.0 0.00 0.00 

22006 R 0.31 0.27 5.4 0.17 368 23.6 0.00 0.00 0.2 0.00 362 24.5 0.10 0.08 

Table A-4

 ------------------Bag 1 (g/mi)------------------ ------------------Bag 2 (g/mi)------------------ ------------------B

FTP Exhaust Results: Bags 1-3
150 21916 F 0.52 0.49 3.7 0.75 375 23.3 0.02 0.01 0.2 0.09 375 23.7 0.07 0.05 

22137 R 0.52 0.49 2.8 0.70 368 23.8 0.01 0.01 0.2 0.08 360 24.7 0.06 0.05 

151 22023 F 0.55 0.49 9.4 0.46 380 22.4 0.01 0.00 0.1 0.03 408 21.8 0.12 0.09 

22081 R 0.51 0.45 7.6 0.53 387 22.2 0.01 0.00 0.0 0.02 409 21.7 0.10 0.08 

152 22013 F 0.38 0.34 6.2 0.21 509 17.1 0.01 0.01 0.0 0.00 504 17.6 0.07 0.06 

22132 R 0.36 0.33 6.0 0.11 504 17.3 0.01 0.01 0.0 0.00 506 17.6 0.05 0.05 

153 22072 F 0.28 0.25 5.8 0.21 368 23.5 0.01 0.00 1.3 0.02 352 25.1 0.02 0.01 

22166 R 0.27 0.25 6.2 0.20 374 23.2 0.00 0.00 0.5 0.01 359 24.7 0.00 0.00 

154 22086 F 0.29 0.27 2.9 0.26 311 28.1 0.05 0.04 2.9 0.00 311 28.2 0.03 0.02 

22177 R 0.30 0.29 2.9 0.28 312 28.0 0.05 0.03 2.7 0.00 309 28.4 0.03 0.02 

155 21155 F 0.21 0.19 2.3 0.29 327 26.8 0.02 0.02 0.1 0.02 309 28.7 0.01 0.01 

22202 R 0.28 0.26 2.7 0.26 330 26.6 0.01 0.01 0.1 0.03 312 28.4 0.02 0.02 

156 22121 F 0.82 0.75 6.0 0.52 476 18.2 0.02 0.01 0.1 0.08 440 20.2 0.09 0.07 

22182 R 0.64 0.60 5.9 0.40 427 20.3 0.02 0.01 0.1 0.03 375 23.7 0.08 0.06 

182 22262 F1 0.59 0.56 3.8 0.87 366 23.8 0.04 0.03 0.2 0.11 358 24.8 0.09 0.07 

22300 R1 0.60 0.03 3.4 0.79 366 23.8 0.01 0.01 0.2 0.09 355 25.0 0.08 0.02 22518 F2 1.37 1.33 5.5 0.85 375 22.9 0.04 0.04 0.1 0.11 366 24.3 0.09 0.08 22578 R2 0.58 0.55 4.3 0.79 367 23.7 0.02 0.02 0.2 0.09 403 22.1 0.08 0.06 

183 22368 F 0.34 0.32 2.8 0.34 445 19.8 0.03 0.02 0.5 0.09 427 20.8 0.07 0.05 

22438 R 0.35 0.32 4.3 0.40 446 19.6 0.01 0.01 0.0 0.09 424 21.0 0.03 0.02 

184 22398 F 0.94 0.72 14.0 0.23 473 17.9 0.21 0.15 5.7 0.00 479 18.2 0.08 0.07 

22463 R 0.48 0.42 6.9 0.29 463 18.7 0.02 0.02 0.5 0.00 477 18.6 0.05 0.04 

185 22414 F1 0.62 0.57 6.8 0.86 508 17.1 0.02 0.01 0.2 0.06 502 17.7 0.06 0.03 

22571 F2 0.60 0.55 6.3 0.83 498 17.5 0.02 0.02 0.2 0.08 527 16.9 0.07 0.04 22471 R 0.56 0.52 7.0 0.92 495 17.5 0.02 0.01 0.2 0.06 491 18.1 0.04 0.02 
186 22612 F 0.76 0.70 9.4 0.76 552 15.6 0.03 0.02 0.1 0.17 572 15.5 0.05 0.02 

22679 R 0.72 0.66 8.4 0.89 549 15.8 0.02 0.01 0.0 0.16 567 15.7 0.06 0.04 

187 22618 F 0.51 0.48 4.7 0.94 654 13.4 0.03 0.02 0.6 0.05 560 15.9 0.03 0.03 

22712 R 0.50 0.47 4.9 0.95 682 12.9 0.03 0.02 0.4 0.07 575 15.5 0.04 0.03 

188 22609 F1 0.23 0.21 4.1 0.16 354 24.7 0.01 0.01 0.6 0.01 335 26.5 0.18 0.18 

22633 R 0.22 0.20 4.5 0.16 365 23.8 0.01 0.01 1.3 0.01 347 25.5 0.01 0.01 22694 F2 0.27 0.25 4.5 0.16 355 24.5 0.02 0.02 1.0 0.01 346 25.6 0.01 0.01 

189 22733 F 0.20 0.18 2.4 0.12 291 30.1 0.01 0.00 0.3 0.04 297 29.9 0.01 0.00 

22763 R 0.22 0.21 1.9 0.20 306 28.7 0.01 0.01 0.2 0.03 293 30.3 0.01 0.01 

190 22859 F 0.76 0.68 13.2 0.30 393 21.4 0.05 0.03 0.5 0.12 398 22.3 0.06 0.04 

22921 R 0.53 0.48 8.2 0.27 384 22.3 0.02 0.01 0.1 0.13 384 23.2 0.03 0.02 

191 22849 F 0.57 0.53 4.6 0.79 653 13.4 0.05 0.04 0.2 0.19 620 14.3 0.04 0.03 

22873 R 0.56 0.53 5.1 0.89 638 13.7 0.03 0.03 0.2 0.10 618 14.4 0.05 0.03 

192 22860 F 0.41 0.38 3.7 0.51 474 18.5 0.01 0.01 0.1 0.03 492 18.1 0.07 0.06 

22931 R1 0.39 0.36 3.1 0.38 456 19.2 0.01 0.01 0.1 0.02 484 18.4 0.06 0.05 22985 R2 0.36 0.34 3.0 0.38 467 18.8 0.01 0.01 0.0 0.01 475 18.7 0.05 0.04 

193 22940 F 0.50 0.46 6.8 0.41 383 22.5 0.04 0.02 0.1 0.02 406 21.9 0.06 0.04 

23005 R 0.64 0.58 11.1 0.27 368 22.9 0.01 0.01 0.0 0.01 405 22.0 0.06 0.05 

194 22959 F 0.61 0.58 4.2 0.27 398 21.9 0.01 0.01 0.1 0.23 390 22.8 0.01 0.00 

23032 R 0.39 0.36 4.1 0.27 391 22.3 0.00 0.00 0.3 0.14 408 21.8 0.05 0.05 
Veh Fuel Failure/

No Profile Repair Initial Bag 1 Bag 2 2 min Bag 3 Bag 4 2 min Bag 5 Bag 6 2 min

140 Target 95.0 101.4 111.6 112.1 115.3 118.0 118.4 121.2 124.8 124.5

Actual F 95.5 99.6 112.7 114.1 115.6 117.8 118.4 122.1 125.6 124.4

Actual R 94.5 99.8 111.7 112.3 115.2 118.4 117.8 122.1 125.4 125.4

141 Target 95.0 99.0 109.5 110.9 117.3 122.2 123.0 125.8 128.9 129.4

Actual F 93.8 99.0 108.6 109.8 116.4 121.5 122.7 124.4 127.3 128.1

Actual R 95.1 99.8 109.0 109.0 116.8 123.6 124.8 125.8 127.0 127.9

142 Target 95.0 97.4 103.8 104.4 108.4 112.3 112.8 115.1 119.3 119.5

Actual F 94.7 95.9 101.4 102.5 105.9 109.8 110.5 113.3 118.2 118.8

Actual R 95.1 95.9 102.0 103.1 107.6 111.3 111.9 114.8 118.2 118.6

143 Target 95.0 97.3 104.3 104.7 108.7 112.2 112.7 114.8 116.8 117.0

Actual F 94.5 99.6 105.9 105.7 108.4 111.5 112.5 115.4 117.6 117.4

Actual R 94.9 98.6 104.7 105.3 108.8 112.1 111.5 114.6 117.2 117.2

144 Target 95.0 99.5 108.7 109.1 113.1 116.3 116.7 119.7 123.6 123.8

Actual F 95.7 102.0 109.0 109.0 113.7 116.2 116.6 121.7 124.4 125.0

Actual R 94.3 99.4 110.0 110.5 114.6 116.2 116.4 120.1 124.6 125.0

145 Target 95.0 102.8 111.1 111.7 114.6 116.4 116.6 118.3 120.6 120.6

Actual F 96.3 100.8 110.5 111.9 115.0 116.4 116.2 117.4 119.4 118.8

Actual R 94.9 98.2 109.6 110.2 115.4 118.4 118.9 119.1 120.5 120.9

146 Target 95.0 100.4 110.8 111.1 113.8 117.5 117.6 120.5 122.5 122.5

Actual F 94.7 101.0 106.4 107.2 111.5 114.6 115.0 119.3 122.3 121.9

Actual R 95.7 100.8 108.6 109.2 114.5 117.4 116.8 120.1 122.5 121.5

147 Target 95.0 101.7 114.5 115.7 122.3 128.1 127.9 130.5 134.2 133.6

Actual F 94.1 102.9 114.5 115.6 121.9 127.5 127.9 131.1 134.6 135.5

Actual R 95.0 105.1 113.9 114.6 122.5 127.9 128.1 131.4 135.4 134.6

148 Target 95.0 97.5 103.8 104.7 109.3 113.7 114.6 117.6 121.4 121.6

Actual F 94.3 99.6 103.5 104.3 109.2 113.7 114.3 116.8 120.9 121.1

Actual R 95.1 99.4 103.3 104.3 109.8 113.1 113.5 115.6 120.9 121.5

149 Target 95.0 98.9 106.3 106.9 110.6 114.6 115.2 117.6 120.5 121.4

Actual F 94.1 101.2 106.2 106.4 110.9 114.3 114.6 117.0 121.3 120.9

Actual R 94.1 100.6 107.4 109.4 111.3 113.7 117.2 116.8 121.3 119.5

150 Target 95.0 99.0 106.9 107.5 115.9 120.9 121.6 123.1 125.5 125.5

Actual F 95.1 102.0 108.4 109.0 112.3 117.8 119.1 126.8 126.0 124.2

Actual R 94.9 103.1 109.0 109.0 112.7 120.1 120.7 130.1 125.4 124.0

Liquid Fuel Temperature at Start or End of Running Loss Segment, Degrees F

Running Loss Segment

Table A-5
151 Target 95.0 99.5 108.7 109.1 113.1 116.3 116.7 119.7 123.6 123.8

Actual F 93.8 99.2 108.2 108.2 112.3 116.4 116.4 119.9 123.0 124.2

Actual R 94.3 99.6 108.0 108.6 113.5 115.8 116.0 119.9 124.6 122.9

152 Target 95.0 98.0 102.4 102.9 106.4 109.9 110.4 113.0 116.0 116.6

Actual F 94.7 97.1 103.1 103.7 106.3 112.1 110.9 112.7 116.2 117.0

Actual R 94.1 97.1 102.7 103.5 106.6 110.0 110.5 112.3 115.4 116.4

153 Target 95.0 99.5 110.7 112.6 116.5 120.0 120.4 122.9 126.6 127.1

Actual F 94.3 100.0 109.8 110.7 116.6 121.5 121.9 124.6 126.0 126.4

Actual R 96.9 101.2 110.4 111.3 117.4 121.3 122.1 124.6 126.2 126.0

154 Target 95.0 100.1 108.4 108.5 113.9 117.5 117.5 120.9 124.3 124.9

Actual F 93.9 105.3 112.3 112.3 113.5 118.0 117.8 121.3 123.8 124.0

Actual R 94.1 102.8 109.0 109.0 113.7 116.8 116.6 120.7 124.2 123.8

155 Target 95.0 103.2 113.5 115.2 117.6 119.8 121.2 124.4 128.3 128.3

Actual F 94.3 102.1 112.5 115.0 118.4 120.7 121.7 125.2 128.1 128.5

Actual R 95.3 102.3 112.3 113.9 116.6 120.7 121.5 122.7 128.1 127.9

156 Target 95.0 99.3 107.0 107.9 110.8 114.9 115.6 117.9 121.5 122.0

Actual F 94.5 98.2 106.6 107.0 109.8 114.5 114.6 118.8 121.9 121.7

R 94.7 98.6 107.2 107.6 110.7 115.2 114.6 118.6 120.3 121.1

182 Target 95.0 99.0 106.9 107.5 115.9 120.9 121.6 123.1 125.5 125.5

Actual F1 94.3 100.6 107.6 107.6 114.1 119.3 121.3 123.4 125.8 127.0

Actual R2 94.5 102.0 107.4 107.6 114.6 119.7 120.7 123.6 126.0 125.6

Actual Diag 94.9 99.0 108.8 110.2 114.5 119.7 120.7 123.8 125.6 125.2

Actual F2 95.9 99.6 108.4 109.4 113.5 119.9 120.7 125.6 126.6 126.2

Actual R2

183 Target 95.0 99.2 106.3 106.8 110.1 111.3 111.0 114.4 118.0 118.5

Actual F 94.5 98.6 107.0 107.0 111.5 112.9 112.9 115.6 118.0 118.4

Actual R 95.7 98.6 107.0 107.6 112.9 114.5 114.5 117.0 119.1 117.4

184 Target 95.0 99.1 107.7 108.7 113.3 117.8 118.4 122.0 125.3 124.9

Actual F 94.9 100.2 107.4 107.8 112.7 117.4 117.0 118.2 120.9 126.6

Actual R 93.8 101.8 107.8 108.2 113.3 116.0 117.4 121.3 126.0 126.0

185 Target 95.0 98.1 104.8 105.2 109.2 113.8 114.0 117.5 121.5 121.6

Actual F1 93.9 98.0 104.3 104.9 108.4 113.9 113.9 116.6 121.7 122.5

Actual F2 94.7 97.9 105.7 104.7 108.4 113.3 114.5 117.4 121.9 121.9

Actual R 94.3 97.7 105.1 104.9 108.6 113.7 114.5 116.8 121.5 122.5

186 Target 95.0 98.9 107.2 107.7 111.8 115.8 116.4 119.3 122.5 122.9

Actual F 96.5 100.6 106.8 107.2 111.3 114.6 115.0 117.8 120.5 121.5

Actual R 95.3 99.0 106.6 107.4 111.1 115.2 115.6 118.8 121.7 123.0

187 Target 95.0 97.4 105.3 105.6 110.3 113.1 113.3 116.7 119.9 120.0

Actual F 95.5 99.0 104.5 106.1 110.9 113.0 114.8 117.2 119.7 120.5

Actual R 95.1 98.4 103.1 104.1 109.8 113.7 114.3 116.6 119.7 120.9
188 Target 95.0 99.5 110.7 112.6 116.5 120.0 120.4 122.9 126.6 127.1

Actual F 96.1 100.0 111.1 111.9 116.4 120.9 120.1 122.7 127.1 126.6

Actual R 95.9 100.4 110.7 110.7 116.2 119.7 119.7 123.4 127.7 127.7

Actual F 95.3 99.4 109.8 111.3 117.4 120.1 119.9 121.3 126.0 127.0

Actual R 95.7 99.4 110.2 111.9 118.0 120.5 120.7 121.7 126.4 126.8

189 Target 95.0 98.5 104.9 105.0 108.3 111.4 111.5 114.5 118.2 118.2

Actual F 95.9 98.6 105.1 105.7 109.2 111.7 117.7 113.7 118.9 118.9

Actual R 95.9 99.4 105.7 105.7 109.0 111.9 111.1 115.0 117.6 117.6

190 Target 95.0 97.5 103.8 104.7 109.3 113.7 114.6 117.6 121.4 121.6

Actual F 94.1 96.7 102.0 103.9 108.4 113.1 113.7 116.0 119.9 120.3

Actual R 94.5 97.5 104.1 104.9 109.6 113.7 113.9 116.8 120.7 120.9

191 Target 95.0 100.3 109.4 110.4 114.6 118.4 119.4 120.6 123.5 123.5

Actual F 93.9 97.5 107.4 107.8 113.1 116.8 118.0 120.7 122.9 122.5

Actual R 93.6 98.8 108.8 108.8 114.1 118.0 118.8 122.1 125.8 125.6

192 Target 95.0 97.6 104.2 104.8 108.8 112.7 112.4 115.2 119.0 119.2

Actual F 93.6 96.1 104.3 105.9 110.4 113.1 113.3 115.2 118.8 119.9

Actual R1 94.1 99.0 105.1 105.7 109.4 112.1 112.1 114.6 119.9 120.3

Actual R2 94.3 97.3 105.7 106.4 110.7 113.1 114.1 115.8 118.9 119.1

193 Target 95.0 99.9 110.7 111.0 114.8 118.5 119.2 123.1 126.7 126.7

Actual F 94.1 99.2 110.2 111.7 116.4 120.1 120.9 124.0 125.8 126.2

Actual R 94.1 99.0 109.6 110.2 115.2 119.9 120.7 122.1 126.2 127.0

194 Target 95.0 99.6 109.1 109.3 113.1 117.9 118.4 121.5 124.8 124.8

Actual F

Actual R 95.1 98.8 109.0 110.0 115.6 117.6 118.2 120.7 127.3 127.7
1 hour max

Enhanced - Purge and load with 

1.5 X working capacity w/butane

ORVR - Load to 2 g 

breakthrough with butane

10 minutes

4 hours max

7 min. max

Figure A-1

9 RVP, 40% full

Canister Pre-conditioning

Start

Fuel Drain, Fill

9 RVP, 40% full

Pre-conditioning Drive

FTP Evaporative Emission Test Procedure

Vehkicle Soak

68 - 86 F

3 Day Diurnal Loss Test

3-24 hour cycles @ 72-95-72 F

End

@ 95 F

Hot Soak Loss Test

1 hour, @ 95 F

Vehicle soak

Last 6 hrs @ 95 F

One UDDS

Fuel Drain, Fill

Cold start exhaust test

Hot start exhaust test

Running Loss Test

UDDS, 2 NYCC, UDDS

12-36 hours

6-36 hours

6-36 hours