Abstract:
A process for testing and the testing assembly for performing the process for testing an anti-lock brake system (ABS) for a vehicle after installation or work on the ABS without the need to test the vehicle for an ABS design braking event. The process involves engaging a testing unit computer to the electrical communication network of the vehicle and communicating with the Electronic Control Module (ECM) of the ABS. The vehicle is driven onto motorized rollers that can roll the wheels at low speeds without requiring vehicle movement. The testing unit computer makes a series of queries to the ECM to determine status of various parameters. Additionally, the portable computer is used to make directives to the ECM as far as cycling the ABS modulating valves such as the ABS hold solenoids and the ABS decay solenoids and the driver as far as braking or releasing the brake. The process is essentially a closed loop test of the completely installed ABS system without actually requiring a wheel lockup at speed to test vehicle response, that is inducing an ABS design event.

Description:
This is a non-provisional application claiming priority under provisional patent application Ser. Nos. 60/102,913, filed Oct. 2, 1998, and 60/130,056, filed Apr. 19, 1999. 
    
    
     BACKGROUND OF INVENTION 
     This invention relates to a process for testing an anti-lock brake system (ABS) for a vehicle after installation or work on the ABS without the need to test the vehicle for an ABS design braking event. The process involves engaging a portable computer to the electrical communication network of the vehicle and communicating with the Electronic Control Unit (ECU) or Electronic Controller Module (ECM) of the ABS. The vehicle is driven onto motorized rollers that can roll the wheels at low speeds without requiring vehicle movement. The portable computer makes a series of queries to the ECU to determine status of various parameters. Additionally, the portable computer is used to make directives to the ECU as far as cycling the ABS hold solenoids and the ABS decay solenoids and the driver as far as braking. 
     SUMMARY OF INVENTION 
     The process is essentially a closed loop test of the completely installed ABS system without actually requiring a wheel lockup at speed to test vehicle response (a “design braking event”). Prior art involved either testing the individual components during various stages of assembly or making the vehicle perform a simulated ABS design braking event to test the system on a wheel lockup. 
     The ABS system on the vehicle is engaged to the electrical communication system of the vehicle that currently may be a J1587 or J1939 electrical network. The ABS system contains the following components for each vehicle wheel: a wheel speed sensor; an ABS hold solenoid; and an ABS decay solenoid. All these components are electrically engaged to the ECU that will be described here as either the ECU or the ECM. The wheel speed sensor generates a signal to the ECU that is proportional to the speed in miles per hour (mph) at which the wheel turns radially. The ABS hold solenoid when closed will lock out the supply of brake actuating fluid, whether it be air or hydraulic, from activating the particular brake on a wheel. Closing the ABS hold solenoid prevents a brake for a particular wheel to be applied. The ABS decay solenoid when closed causes the brake actuating fluid, whether it be air or hydraulic, to be released from application on the brake for a particular wheel. Opening the ABS decay solenoid will cause a brake for a particular wheel to be released. Under an ABS design initiation event where a wheel is locked up, the ECU of the ABS system will cycle the hold solenoid and the decay solenoid to mitigate or release the wheel lockup. 
     The testing equipment required for performing the process includes motorized wheel rollers that may be controlled through an external computer such as the manufacturing or maintenance facilities main computers. The rollers may rotate one or two wheels of an axle at a time or simultaneously and each contains a counter torque measuring apparatus which measures the vehicle wheel&#39;s resistance to movement. This resistance may be brought on by application of vehicle brakes or due to mechanical binding within the axle or brake. The portable computer for engagement to the electrical communication system of the vehicle and querying the ECU is comprised of an off-the-shelf portable computer (PC) engaged to a bar code scanner for reading the vehicle identification number (VIN) and a touch control screen for operation of the PC. In the preferred embodiment, the PC has a pentium processor and the bar code scanner and the touch control screen are powered from the keyboard connector of the PC. 
     The process contains the following steps: 
     1. The vehicle is located such that the a right side and a left side wheel for one axle rest each on one of the motorized rollers; 
     2. The portable PC is electrically connected to the onboard electrical communication network of the vehicle, preferably by plugging a connector into an outlet in a cab of the vehicle; 
     3. The PC queries the ECU as to the configuration of the ABS; 
     4. The PC compares the configuration from the ECU with the configuration associated with the specific vehicle as provided by the main facility testing computer, which may be a main frame computer; 
     5. If the configuration of the ABS recorded in the ECU differs from the main frame expected configuration, the PC directs the ECU to self query the components of the ABS through the onboard network; 
     6. If the configuration of the ABS on of step 4. or self checked in step 5. matches with the main frame expected, the configuration passes, otherwise the configuration fails; 
     7. The PC directs the ECU to report battery voltage with the voltage passing if at above a preset quantitative value, preferably twelve (12) volts; 
     8. The PC queries the ECU for the existence of any active faults within the ECU as defined by a Society of Automotive Engineering (SAE) standard, if no faults exist the ECU passes; 
     9. The correctness of left/right side connections to the ECU is verified when the rollers commence slowly rolling one of the wheels, preferably the right wheel of the axle, as the PC looks for the ECU to report that only the right (rolled) wheel is rolling at a particular speed, preferably slower than five (5) mph; 
     10. Without the drivers foot on the brake pedal, the rollers then commence rolling both of the wheels on the axle to be tested at a similar speed while the counter torque measuring devices on the motorized rollers measure resistance of the wheels against turning; 
     11. If the resistance of the wheels against turning does not rise above a pre-selected value, then the axle to be tested and brakes pass the mechanical binding test; 
     12. The rollers commence rolling the left wheel with the PC looking for the ECU to now report that both left and right wheels of the tested axle are rolling; 
     13. If both steps 11 and 12. show that the expected wheels rolled as detected by the ABS then the left/right side connections are passed; 
     14. The PC then alternatively directs the ECU to cycle the ABS hold solenoids for each of the wheels with the PC continuously querying the ECU as to brake actuating fluid pressure for each wheel, while the hold valve is closed the PC directs the driver of the vehicle to press constantly on the brake pedal, a passing hold solenoid being one where the downstream pressure does not increase upon the application of actuating fluid on the upstream side of the hold valve; 
     15. The PC then directs the driver of the vehicle to press constantly on the brake pedal while the PC then alternatively directs the ECU to cycle the ABS decay solenoids for each of the wheels with the PC continuously querying the ECU as to brake actuating fluid pressure for each wheel, a passing decay solenoid being one where the actuating pressure decreases to zero upon the cycling open of the ABS decay solenoid; 
     16. With the motorized rollers rotating both wheels simultaneously, the counter torque measuring devices of the motorized rollers, the PC directs the driver of the vehicle to apply constant pressure on the brake pedal; 
     17. The main frame computer compares the counter torque measured for each wheel to determine: (a) whether the brake for each wheel is providing sufficient braking power above a preset level, and (b) to compare the braking power between the two wheels to ensure the difference between the brakes does not exceed a preset level of difference in braking power; 
     18. Should both sub-steps of step 17 be within the specifications, the brakes are passed; 
     19. The vehicle is relocated to test another drive axle of the vehicle and steps 10 to 18 are repeated for the second drive axle with additional drive axles being tested similarly; and 
     20. A report indicating which test, passed or failed, is issued. 
     21. The process may be varied without departing from the main intent of the invention that is to test an ABS system on assembly without putting the system through a design-braking event. 
    
    
     DRAWINGS 
     Other objects and advantages of the invention will become more apparent upon perusal of the detailed description thereof and upon inspection of the drawings, in which: 
     FIG. 1 is a mobile vehicle with an antilock brake system to which a process performed in accordance with this invention may tested without the vehicle undergoing an antilock braking design event. 
     FIG. 2 is a system for performing an antilock brake system assembly verification made in accordance with this invention. 
     FIG. 3 is a process of verifying antilock brake system assembly in a mobile vehicle in accordance with this invention. 
     FIG. 4 is a portable embodiment of a testing unit used for verifying assembly of an antilock brake system for a mobile vehicle. 
     FIG. 5 is first portion of a further embodiment of a process of verifying antilock brake system assembly in a mobile vehicle in accordance with this invention. 
     FIG. 6 is a continuation of the process shown in FIG.  5 . 
     FIG. 7 is a continuation of the process shown in FIG.  6 . 
     FIG. 8 is a continuation of the process shown in FIG.  7 . 
     FIG. 9 is a continuation of the process shown in FIG.  8 . 
     FIG. 10 is a continuation of the process shown in FIG.  9 . 
     FIG. 11 is a continuation of the process shown in FIG.  10 . 
     FIG. 12 is a continuation of the process shown in FIG.  11 . 
     FIG. 13 is a continuation of the process shown in FIG.  12 . 
     FIG. 14 is a continuation of the process shown in FIG.  13 . 
     FIG. 15 is a continuation of the process shown in FIG.  14 . 
     FIG. 16 is a continuation of the process shown in FIG.  15 . 
     FIG. 17 is a continuation of the process shown in FIG.  16 . 
     FIG. 18 is a continuation of the process shown in FIG.  17 . 
     FIG. 19 is a continuation of the process shown in FIG.  18 . 
     FIG. 20 is a continuation of the process shown in FIG.  19 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a mobile vehicle  101  with an antilock brake system to which the processes and testing system of FIGS. 2 to  5  may be used upon to verify assembly of the antilock brake system. 
     The vehicle  101  may be an automobile, a medium or heavy duty truck, or people transportation bus such as a school bus. The vehicle has a chassis  102  to which a rear axle  107  and a front axle  108  are engaged to through a suspension. An engine  103  engaged to a transmission  104  is engaged to the chassis  102 . The transmission is engaged to at least the rear axle  107  through a drive-line  105  and differential  106 . Each axle has at least two wheels  109 , one engaged to each rotatable end of the axles. Each wheel  109  has an actuating fluid brake actuator, cylinder, or chamber  112  which when the actuating fluid, whether it be air or hydraulic fluid, is removed will apply braking force to the associated wheel  109  to cause the wheel to slow it rotational motion and eventually stop. Each brake actuator  112  has a brake system actuating fluid source or supply  110  through modulating valves. The modulating valves may be a hold valve  115  and a decay valve  116 . When air is the actuating fluid, the fluid source  110  is a vehicle air tank. The hold valves  115  and the decay valves  116  may be electrical solenoid valves. Additionally, the hold valve  115  and the decay valve  116  may be the same valve or on a single manifold. For hydraulic systems, hold valves  115  and decay valves  116  may all be mounted on a single manifold, whereas in air brake systems the hold valve  115  and decay valve  116  are mounted close to the associated wheel  109 . Each hold valve  115  is inline with the supply of actuating fluid such that when the hold valve  115  is closed actuating fluid is denied to the associated brake cylinder  112  thereby locking the braking force on the associated wheel  109 . Each decay valve  116  is engaged to the brake cylinder  112  or supply of actuating fluid such that actuation or opening of the decay valve will cause actuating fluid to be bled off of the associated brake cylinder  112  thereby removing braking force from the associated wheel  109 . The vehicle has an antilock brake electronic control module (ECM)  111  electrically engaged and for controlling the hold valves  115  and the decay valves  116 . The control over these valves allows the antilock brake ECM  111  to adjust braking force on the individual wheels to remove a detected wheel lockup condition. Radial speed sensors  114  in general provide wheel lockup and wheel speed information. Each wheel  109  has a radial speed sensor  114  that is electrically engaged to the antilock brake ECM  111 . The radial speed sensor  114  may monitor a tooth wheel  113  engaged to the associated wheel  109 . Installation of the radial speed sensors  114  is important for antilock brake system operation and performance. Incorrect installation may result in inaccurate radial speed indications for the individual wheels  109 . 
     The vehicle  101  has an internal electronic network data link  119 , shown in FIG.  2 . The antilock brake ECM  111  is engaged to communicate along the data link  119 . The data link  119  may operate under the Society of Automotive Engineers (SAE) communication protocols J1587, J1850, or J1939 or any allowable combination or subsequent revision of these protocols by the SAE. Electronic control modules for other vehicle components such as the engine  103  and transmission  104  may also communicate with and be in electrical engagement with the data link  119 . The data link  119  may have a plug-in connection  119 a to which electrical devices that may communicate under the communication protocols may be engaged. 
     A system for verifying assembly of an antilock brake system made in accordance with this invention may be used as a vehicle end-of-assembly-line final check for antilock brake systems or as a post maintenance assembly check for a brake repair facility. The main assumption for such a system made in accordance with this invention is that the manufacturer of the antilock brake ECM  111  has properly programmed the antilock brake ECM  111  for the design antilock braking event. Under that assumption, the system and process that it controls for verifying antilock brake system need only verify proper connections and communications between components. In the prior art, vehicles had to be accelerated to higher speeds on the order of 20 to 35 miles per hour with a design antilock brake event induced. The system and process of this invention only need have the vehicle wheels  109  rolled on the order of 3 to 6 miles per hour. Unlike the prior art, extensive safety precautions for testing an accelerated and subsequently decelerated vehicle indoors are not required. Additionally, the assembly or maintenance facility does not need to be concerned with removal excessive exhaust fumes generated indoors by the higher speed tested vehicles of the prior art. 
     A system for verifying assembly of an antilock brake system made in accordance with this invention is shown in FIG.  2 . The system includes a testing unit  160  that is electrically engageable to the internal electronic network data link  119  of the vehicle  101 . The testing unit  160  shown in FIG. 2 is a portable version although testing units  160  for this invention may fixed so long as they may communicate with the antilock brake ECM  111 . The testing unit  160  is shown electrically engaged to the data link  119  through the plug-in connection  119   a  of the data link  119  on the vehicle  101 . The antilock brake assembly verification system also includes a data management system  150  that may be a main frame computer although any computing system with sufficient capacity will be acceptable. In a small brake maintenance facility the testing unit  119  and the data management system  150  may be the same processor. The data management system  150  will contain a data base of the expected configurations the vehicles that will have their antilock brake system assemblies verified. The portable testing unit  160  shown in FIG. 2 has a wireless communication unit  162  that allows communication between the testing unit  160  and the data management system  150 . This wireless communication may be by radio waves. If the testing unit  160  is a fixed embodiment, the communication would be hard wired to the data management system  150 . The data management system  150  is engaged to control a pair of roller mechanisms  151  or as will be referred to as rollers  151 . The rollers  151  are spaced to allow vehicles  101  of various axle lengths and wheel dimensions to be driven or moved onto so that a wheel on either side of the axle to be tested is in contact with the turn cylinders  152  of the roller  151 . The rollers  151  will rotate the wheels  109  together or independently per the instructions from the data management system  150 . The rollers  151  contain resistance to turning measuring devices that provide a resistance or counter torque force against turning back to the data management system. When the brakes of the vehicle  101  are not applied, the resistance to turning measurements are indications of the bearings of the wheels  109  and brake tightness and other components on the axle for enabling free wheeling. When the brakes of the vehicle are applied, the resistance to turning measurements indicate braking strength. Comparison of the resistance to turning measurements between the wheels  109  with the brakes applied will indicate imbalances between the braking ability at each wheel  109 . The data management system  150  is also engaged to a driver prompt sign  153 . This driver prompt sign  153  is in a prevalent location to a driver of the vehicle with an axle engaged on the rollers  151 . The driver prompt sign, provides instructions to the driver such as when to apply the brakes of the vehicle  101  through the brake pedal. The driver prompt sign  153  also contains queries to the driver such as to identify which axle is being tested, and to what indicators are lit in a cab of the vehicle  101 . Sample instructions and queries displayed on the driver prompt sign  153  are discussed below in the description of the process. The data management system  150  is also engaged to a set of brake system pressure gauges  154  that in some cases may be integral to the driver prompt sign  153 . The process involves measurements of antilock brake system actuating fluid pressures from the antilock brake ECM  111 . The pressure gauges  154  which are also visible to a driver of the vehicle from the cab of the vehicle  101  during the test provide the driver with some indications of what the system is detecting as to status of the antilock brake system being tested. 
     The testing unit  160  shown in FIG. 4 is a portable embodiment. It contains a portable computer (PC)  161  that is preferably at a minimum a pentium processor as far as processing speed. The PC  161  may be engaged to a vehicle plug-in connector  167  for engagement to the vehicle plugin connector  119   a  and communication with the internal electronic network data link  119 . Communication is accomplished through an interface unit  166  engaged to the PC  161 . The power for the PC  161  is from an internal battery  165  for stand-alone use. When engaged to a vehicle the plug-in connector  167  allows for power flow to power the PC  161  and charge the battery  165  from the vehicle  101  electric system. There may be a power converter  168  to change the normally 12 volt vehicle power to a voltage appropriate for the PC  161 . The PC  161  may be engaged to communicate with a scanner  163 . The scanner  163  is capable of reading the vehicle identification number or VIN of the vehicle  101  to identify the vehicle  101  to be tested. The scanner  163  may be a bar code scanner for vehicles that have their VIN displayed in bar code form. The scanner  163  may be powered from a low voltage power source from the PC  161  as shown in the Figure. The PC  161  may be engaged to a touch screen controller  164  through a PCMCIA card. The driver of the vehicle may answer prompts from the driver prompt sign  153  on the touch screen  164 . The touch screen may also be powered from a low voltage power source such as the PC  161  as shown. Where the PC  161  is not hard wired to the data management system  150 , as in the case shown, the PC  161  will be engaged to a wireless communication device  162  such as the radio shown FIG. 4, through a PCMCIA card. The wireless communication device  162  may also be a microwave transceiver. The testing unit  160  may be programmed with the antilock brake system assembly verification application. This may be written as a 32 bit programming application. The testing unit  160  may be used for other vehicle testing applications beyond the described antilock brake verification, depending on the programming. Two such examples are briefly described as the queries and communications with electronic control modules for the engine  103  and the transmission  104 . One embodiment of the portable testing unit embodiment  160  has been made with a Toshiba Libretto  7 OCT as the PC  161 , touch screen  164  from ELO, and a radio and LAN adapter  162  from Aironet. 
     It should also be noted that the data management system  150  may be the lead processor for the process communicating to the vehicle  101  through the testing unit  160 . 
     A basic process performed to verify the assembly of an antilock brake system in accordance with this invention includes the following steps. The testing unit  160  is engaged to the internal electronic network  119  of the vehicle  101 . The testing unit  160  verifies that the internal electronic network  119  is electrically active and that there is communication with the antilock brake ECM  111 . This portion of the test is considered failed if either the network is not active or if there is no communication with the antilock brake ECM  111 . The testing unit  160  queries the antilock brake ECM as to the specific vehicle antilock brake system configuration and compares that configuration with one received from the data management system  150 . The configuration check is passed if there is a match and is failed if there is no match. The ECM  111  may be directed to recheck configuration if there is no match initially, and may be later passed if such a re-check then results in a match with the data management system  150  expected configuration. The testing unit  160  queries the antilock brake ECM  111  if the ECM  111  has any self identified faults to which the specific ECM  111  manufacturer has programmed the ECM  111  to identify and flag. The ECM self identified check is passed if no faults are identified, and failed if a fault is identified. The testing unit through the data management system or the data management system leading will direct alternatively direct the rollers  151  to roll each wheel  109  for the axle to be tested, measuring wheel speed from the vehicle&#39;s radial wheel speed sensors  114 . If the speed is within a preset range, the free wheeling speed check is passed, otherwise it is considered failed. Concurrently to, or before, or after the radial speed free wheeling check, the resistance to turning each wheel is measured by the rollers with the rollers turning and the brakes not applied and reported back to the testing unit  160  or data management system  150 . These checks verify that vehicle  101  components that allow the wheels  109  to free wheel are operational and that the brakes were not installed too tight as to allow free wheeling. The driver of the vehicle  101  is prompted or directed to apply the brakes of the vehicle. The testing unit  160  directs the antilock brake ECM  111  to alternatively cycle the brake modulating valves for each wheel with the brakes applied, measuring brake actuating fluid pressure to verify operation and correct installation of each valve. For the vehicle shown in FIG. 1, the modulating valves comprise a hold valve  115  and a decay valve  116 , although other configurations exist. In the case of the hold valves  115  of the FIG. 1 embodiment, closure of the hold valve for the wheel should result in actuating pressure downstream of the hold valve staying the same. The hold valve check is passed if the pressure stays at the previous pressure within a preset tolerance and passed if the pressure is out of the preset tolerance range from the previous pressure. In the embodiment of the test as described, the individual hold valve is closed, and then driver is directed to apply the brakes, the initial downstream pressure being zero, the pressure should stay near or at zero. Where the modulating valves include decay valves  116 , the actuating or opening of the decay valves should result pressure upstream of the decay valves decreasing to below a preset value. The decay valve check is passed if the pressure decreases to below the decay valve preset value and failed if the pressure is at or above the decay valve check preset value. 
     The basic process may be programmed into a computer or a testing unit  160  or the program may be a computer program product comprised of a computer usable medium having computer readable program code means embodied in the medium for affecting the above process when used in conjunction with a testing unit  160 . 
     Additional steps may include the step of measuring resistance to turning the wheels, with the rollers  151  attempting to roll the wheels with the driver applying the brakes. This step will indicate the braking force of the brakes for each wheel  109 . The brake force check will be passed if brake for force for a wheel is above a preset brake force minimum and failed if insufficient force. An additional test includes comparing the brake force between the wheels at opposite ends of an axle. The brake force differential test is passed if the difference is below a maximum preset force differential value and failed if above or at the maximum preset differential value. 
     Additional steps, as shown in FIG. 5 may include the following. As medium and heavy duty trucks may have engine brakes that utilize back-pressure of engine exhaust gases to slow the engine  103  and hence provide braking to the vehicle  101 , these engine brakes would need to be disabled unless they are a component of the antilock brake system. The additional step would be to query the vehicle or a lead electronic control module (lead ECM) on the vehicle to determine if the vehicle has an engine brake. If the response is that is there is an engine brake, then the testing unit  160  directs the component controlling the engine brake to disable the engine brake. If the engine brake will not disable, the check is failed, otherwise it is passed. An additional step may be for the testing unit  160  to query as to the ECM  111 , or ECU for Electronic Control Unit as shown in FIG. 5, as to the ECU part number and ECU serial number. The testing unit will compare the ECU  111  manufacturers correct firmware or internal programming code to be the expected code as received from the data management system  150 . The ECU firmware check will be failed if the firmware is incorrect. 
     The verification of assembly described above only verified antilock brake assembly for one axle of the vehicle. As mentioned above, the are at a minimum two axles on the vehicle  101  and there well could be more. The test described above would be additionally performed on the additional axles. The vehicle  101  would be initially moved or driven onto the rollers  151 , the driver would be queried through the driver prompt sign  153  or the PC  161  as to which axle is being tested on the touch screen  164  or the PC  161  directly The above tests on the applicable axle, wheels  109 , brakes, and modulating valves and then the vehicle would be moved to place a different axle to be tested on the rollers  151  at the direction from the testing unit  160  once again through the prompt sign  153  or the PC  161 . The system would query as to which axle is being tested. If the verification system is checking a drive axle such as the rear axle  107  shown in FIG. 1, the system would query as to whether the vehicle  101  has an automatic traction control (ATC) system. If the answer is yes than the testing unit  160  queries the ATC is inactive. If the ATC system will not go inactive, then the ATC check is failed. Additional steps may verify the ATC system for self detected faults. These steps may include notifying the driver that ATC will be checked, querying the ATC Modulator as to any faults self detected by the ATC modulator. If faults exist the ATC modulator check is failed, otherwise it is passed. Following the checks of both axles, the prompt sign  153  or the PC  161  may direct the driver to release the brakes of the vehicle  101  by removing his foot from the brake pedal. The antilock brake assembly verification system may query the driver if an ‘ABS warning light (is) off?’ in the cab of the vehicle  101 . If the answer back is ‘No’ the antilock brake system warning light off test is failed, otherwise it is passed. The testing unit  160  may then direct the antilock brake ECM  111  to energize the ABS warning light in the cab. The driver would then be queried as to whether the ‘ABS warning light (is) on ?’. The warning light on check is passed if the driver acknowledges ‘Yes’ that the light is on, other wise the warning light on check is failed. An additional test may be that the testing unit  160  may query the antilock brake ECM  111  as to what battery voltage is for the vehicle electrical system. If the voltage is within a preset voltage range the battery check is passed, otherwise the test is failed. An additional step may be the testing unit querying the antilock ECM  111  as to whether current faults are cleared. If current faults are not cleared, the antilock ECM  111  is directed to clear the current faults. The system directs the driver to move the vehicle away from the testing assembly, stores the results, and prints the results if desired. 
     A further step may include querying the engine electronic control module as to the status of the link of the electronic control module of the engine  103  to the internal electronic network  119 . If the link to the network is acceptable the engine link test is passed, otherwise the test fails. A similar check can be run with the electronic control module of the transmission  104 . 
     As described above, the antilock brake system assembly verification system, the process for verifying assembly, and the testing unit for verifying provide a number of advantages, some of which have been described above and others of which are inherent in the invention. Also modifications may be proposed to the antilock brake system assembly verification system, the process for verifying assembly, and the testing unit without departing from the teachings herein.