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    GM Lumina/Grand Prix/Cutlass Supreme/Regal 1988-1996

    Testing

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    SERVICE PRECAUTIONS




    CAUTION
    This brake system uses a hydraulic accumulator which, when fully charged, contains brake fluid at very high pressure. Before disconnecting any hydraulic lines, hoses or fittings be certain that the accumulator pressure is completely relieved. Failure to depressurize the accumulator may result in personal injury and/or vehicle damage.



    Certain components within the ABS system are not intended to be serviced or repaired individually. Only those components with removal and installation procedures should be serviced.
     
    Do not use rubber hoses or other parts not specifically specified for the DM ABS-III system. When using repair kits, replace all parts included in the kit. Partial or incorrect repair may lead to functional problems and require the replacement of the Powermaster III.
     
    Lubricate rubber parts with clean, fresh brake fluid to ease assembly. Do not use lubricated shop air to clean parts; damage to rubber components may result.
     
    Use only DOT 3 brake fluid from an unopened container. Use of DOT 5 silicone brake fluid is not recommended; reduced system performance or durability may result.
     
    If any hydraulic component or line is removed or replaced, it may be necessary to bleed the entire system.
     
    A clean repair area is essential. Perform repairs after components have been thoroughly cleaned; use only denatured alcohol to clean components. Do not allow ABS components to come into contact with any substance containing mineral oil; this includes used shop rags.
     
    Remove the lock pin before disconnecting CPA connectors at the Powermaster III.
     
    The Anti-lock brake controller is a microprocessor similar to other computer units in the vehicle. Insure that the ignition switch is OFF before removing or installing controller harnesses. Avoid static electricity discharge at or near the Controller.
     
    Fault codes stored within the system can only be read with a bi-directional scanner such as GM 9400100-A (Tech 1 Diagnostic Computer) or equivalent. Some scanners will require an additional cartridge (GM 9400008-A or equivalent) to read the system.
     
    The brake controller is equipped with on-board diagnostic programs beyond the setting of codes. Not all scanners are capable of using these other features. Consult the scanner manufacturer's manual for directions and capabilities.
     

    PRE-DIAGNOSIS INSPECTION



    A visual check of specific system components may reveal problems creating an apparent ABS malfunction. Performing this inspection may reveal a simple failure, thus eliminating extended diagnostic time. The steps should be performed in order.

    1. Depressurize the Powermaster III.
    2.  
    3. Inspect the brake fluid level in the reservoir.
    4.  
    5. Inspect brake lines, hoses, Powermaster III and brake calipers for leakage.
    6.  
    7. Visually check brake lines and hoses for excessive wear, heat damage, punctures, contact with other parts, missing clips or holders, blockage or crimping.
    8.  
    9. Check the calipers and pins for rust or corrosion. Check for proper sliding action.
    10.  
    11. Check the caliper pistons for freedom of motion during application and release.
    12.  
    13. Inspect the front wheel speed sensors for proper mounting and connections.
    14.  
    15. Inspect the front speed sensor rings for broken teeth or poor mounting.
    16.  
    17. Measure front wheel speed sensor to ring air gap. Air gap is not adjustable but should be 0.019-0.068 in. (0.5-0.17mm).
    18.  
    19. Inspect rear wheel speed sensors for proper installation or damage. Inspect rear speed sensor wiring connections.
    20.  
    21. Brake pedal travel should not bottom near the floor after Powermaster III is depressurized.
    22.  
    23. Check for worn or missing isolator bushings on Powermaster III which may cause or amplify pump motor noise.
    24.  
    25. Inspect the high pressure line on Powermaster III which may be contacting other engine compartment components.
    26.  

    TROUBLE CODES



    See Figures 1 and 2

    Click image to see an enlarged view

    Fig. Fig. 1: List of ABS Diagnostic Trouble Codes (DTCs) - 1988-91 vehicles



    Click image to see an enlarged view

    Fig. Fig. 2: List of ABS Diagnostic Trouble Codes (DTCs) - 1988-91 vehicles, continued

    The Anti-lock Brake Controller contains diagnostic capabilities which can identify faults specifically including whether or not the fault is intermittent. The diagnostics must be read with a bi-directional scanner.

    There are 58 possible 4-digit fault codes. The first 5 codes generated are stored in the order in which they occurred from least to most recent. Fault codes will not disappear when the ignition is turned OFF or the battery cable is disconnected. If no further fault codes occur within 50 driving cycles (Ignition switch ON and vehicle speed over 10 mph) the controller will clear the memory.

    In order to access the trouble codes, connect a bi-directional scan tool to the ALDL connector and follow the scan tool manufacturer's instructions to read the codes. The ALDL connector is located behind the instrument panel to the right of the steering column.

    A current code indicates that the malfunction occurred during the current ignition cycle. After all current codes have been displayed, the history codes will be displayed. History codes are malfunctions which do not currently exist, but could possibly aid in determining the cause of an intermittent condition.

    Always turn the ignition switch OFF prior to initial troubleshooting to ensure all diagnostic data is preserved. If the ignition is not turned OFF prior to reading fault codes, any information stored for a fault in the last drive cycle will be lost.

    The hand scanner must be used to clear trouble codes from the memory after repairs are completed.

    ADDITIONAL DIAGNOSTIC CAPABILITIES



    Not all scanners can use the additional diagnostics within the controller. Consult tool manufacturer's instructions for correct application and use.

    ABS Data List

    : allows data parameters for many circuits to be monitored. This feature can be particularly helpful in tracking intermittent problems.

    ABS Snapshot:

    will store the ABS data list parameters for a period of time before, during and after a fault triggers a code. Snapshot may be set for a specific code, any ABS code or at operator's command.

    Manual Relay and Solenoid Control:

    allows the front and rear enable relays and the individual hold and release solenoids to be commanded ON or OFF. Feature will display actual output or voltage (HIGH or LOW) at that particular terminal on the controller. Solenoids can only be energized for about 40 seconds; they will then be turned OFF for purposes of cooling.

    Enhanced Diagnostics:

    used to determine if a trouble code is intermittent, identify how intermittent it is and give information regarding vehicle operating conditions when the most recent trouble code was set. The following data can be displayed:



    How often each of the 5 stored codes occurred. Example: A code which set once in the last 35 driving cycles might indicate a one-time occurrence such as a severe pot-hole.
     
    The speed the ABS controller sensed the vehicle travelling when the last fault occurred.
     
    State of the brake switch (ON, OFF or OPEN) at time of the last fault occurrence. Only the state of the switch is known; no information on braking or deceleration is given.
     
    Brake system fluid pressure.
     
    Whether or not brake pedal had been applied during this driving cycle. If no application is seen, fault may have been detected when ignition was turned ON .
     
    Whether or not ABS stop was in progress when fault occurred.
     
    How many drive cycles have occurred since last code was set.
     

    INTERMITTENTS



    The diagnostic procedures may or may not be helpful in determining the cause of intermittent problems in the system electrical components. In most cases, the fault must be present to locate.

    Most intermittent problems are caused by faulty electrical connections or wiring. When an intermittent failure is encountered:

    1. Check for history codes which may be stored in the anti-lock brake controller. If a history code is stored, this may indicate the circuitry which has the intermittent condition. Move the related connectors, harness and components in an effort to induce the failure.
    2.  
    3. Enter the Enhanced Diagnostic feature. This feature will help determine how intermittent the fault is and may help determine certain conditions that cause the fault.
    4.  
    5. Set the ABS snapshot to trigger on the intermittent trouble code and use the enhanced diagnostic feature to recreate the conditions that cause the intermittent code to set.
    6.  
    7. Check for poor mating of connector halves or terminals not fully seated in the connector body.
    8.  
    9. Inspect for improperly formed or damaged terminals. All connector terminals in a problem circuit should be carefully reformed to increase contact tension.
    10.  
    11. Check for poor terminal-to-wire connection. This requires removing the terminal from the connector body to inspect.
    12.  

    HYDRAULIC DIAGNOSIS



    The Anti-lock Brake Controller must be scanned for trouble codes before attempting any of the following diagnostic procedures.

    If no codes have been set, the tests must be performed in the alphabetical order given. Always perform the pre-diagnosis inspection before any other testing is begun.

    Test A - ABS System Functional Check
    1. Properly connect a scanner to ALDL connector.
    2.  

    An assistant must sit in the driver's seat and operate the brakes and hand scanner during testing.

    1. Raise and safely support the vehicle.
    2.  
    3. Turn ignition switch ON and put transmission in P . Do not apply the brakes. Attempt to rotate each wheel by hand. If any wheel does not rotate, inspect for correct operation of parking brake or calipers.
    4.  

    The rear wheels should turn with little or no resistance. The front wheels will have some resistance caused by driveline and differential drag. This is normal. If the wheel can be turned with normal hand force, the condition is acceptable.

    1. Apply medium pressure to the brake pedal. Attempt to rotate each wheel again; no rotation should be possible.
    2.  
    3. If either of the front wheel rotate, replace the Powermaster III; the front master cylinder portion is malfunctioning. If either of the rear wheels rotate, a Low or No Boost Pressure condition exists; refer to Test C.
    4.  
    5. Apply the service brakes with moderate effort and use the hand scanner to energize the hold and release solenoids for a specific wheel. Check the wheel for rotation. While some drag may be present due to residual line pressure, the wheel should rotate with hand force. Repeat this step for other wheels.
    6.  
    7. While the solenoids are energized, the brake pedal should not sink steadily to the floor, the pump should not run constantly or frequently, and the sound of fluid being forcefully sprayed in the reservoir should not be heard. If any of these conditions occur, check the wiring and connections to the appropriate solenoid. If any wires or connectors are found damaged, replace the Powermaster III wiring harness.
    8.  
    9. If the any condition in the previous step recurs after replacing the wiring harness, replace the Powermaster III unit.
    10.  

    Test B - ABS Hold Function Check
    1. Properly connect hand scanner to ALDL connector.
    2.  

    An assistant must sit in the driver's seat and operate the brakes a scanner during testing.

    1. Raise and safely support the vehicle.
    2.  
    3. Turn ignition switch ON and put transmission in N . Keep transmission in N throughout testing. Allow ABS unit to pressurize before proceeding.
    4.  
    5. Use the scanner to energize only the rear hold solenoid, then apply the brakes moderately.
    6.  
    7. Attempt to turn a rear wheel; it should turn freely for 6 or more seconds before the brakes apply.
    8.  
    9. While the solenoid is energized, the brake pedal should not sink steadily to the floor, the pump should not run constantly or frequently, and the sound of fluid being forcefully sprayed in the reservoir should not be heard.If any of these conditions occur, or if the brakes apply in 5 seconds or less, replace the rear solenoid assembly in the Powermaster III and retest the system. If similar conditions still exist, replace the Powermaster III unit.
    10.  
    11. Moderately apply the brakes and use the hand scanner to energize the hold function of 1 of the front wheels.
    12.  
    13. Attempt to turn the appropriate front wheel; it should turn freely for 6 or more seconds before the brakes apply.
    14.  
    15. While the solenoid is energized, the brake pedal should not sink steadily to the floor, the pump should not run constantly or frequently, and the sound of fluid being forcefully sprayed in the reservoir should not be heard. If any of these conditions occur, or if the brakes apply in 5 seconds or less, replace the proper solenoid assembly in the Powermaster III and retest the system. If similar conditions still exist, replace the Powermaster III unit.
    16.  
    17. Repeat the testing procedure for the other front wheel.
    18.  

    Test C - Low or No Boost Pressure Check
    1. With ignition OFF , depressurize the Powermaster III unit completely.
    2.  
    3. Properly connect a scanner to the ALDL connector.
    4.  
    5. Use the hand scanner to activate the pump. Note the total pump running time; this is the amount of time between ignition on and pump shut- OFF.
    6.  
    7. If the total time is 40 seconds or less, the Powermaster III is developing satisfactory boost pressure. If the running time is greater than 40 seconds, perform Test D.
    8.  
    9. Determine the pump OFF time by moderately applying the brakes and holding the brake pedal down. Use a stopwatch to measure the time between brake application and pump engagement.
    10.  

    Some a scanners can compute this time using the bleed-down check function.

    1. If the pump OFF time is 50 seconds or less, a problem may exist within the Powermaster III. Refer to Test E. If the pump OFF time is greater than 50 seconds, the Powermaster III is holding boost pressure satisfactorily.
    2.  

    Test D - Pump Run Time Too Long
    1. With ignition OFF , disconnect the wiring harness at pump connector. Turn the ignition switch ON .
    2.  
    3. Use a digital volt/ohmmeter (DVOM) to check voltage of Pin A to ground. If less than 12 volts, check the battery, charging system and non-ABS circuits for damage.
    4.  
    5. Turn the ignition switch to OFF and reconnect the pump harness to the connector. Depressurize the Powermaster III unit.
    6.  
    7. Remove the accumulator and install pressure gauge J-37118 or equivalent. Install the accumulator on the pressure gauge adapter.
    8.  
    9. Bleed the Powermaster III at the bleeder valves or use the hand scanner to perform ABS Solenoid Bleed and Checkout Test.
    10.  
    11. Observe the pressure gauge while turning ignition ON . The system should pressurize from 0-500 psi (0-3448 kPa) or greater almost immediately after the ignition is switched on.
    12.  
    13. If the correct pressure is not reached, the accumulator is not holding sufficient precharge and must be replaced.
    14.  
    15. Allow the pump motor to run and and note the pressure at which it either stops or reaches the high-pressure limit. If the indicated pressure is greater than 2900 psi (19,995.5 kPa), the pressure switch is faulty.
    16.  
    17. Using the hand scanner, monitor the pump state while applying the brakes slowly 1-3 times. Note the low pressure at which the pump engages. The pump should turn on at or above 2000 psi (13,790 kPa). If it turns on at a lower pressure, the pressure valve must be replaced.
    18.  
    19. If the pressure switch functions properly, depressurize the Powermaster III completely. Remove the reservoir cover. Do not apply the brakes with the reservoir cover removed.
    20.  
    21. Visually check the pump outlet in the reservoir to be sure it is not clogged. If the outlet is clear, attach 1 end of a clear plastic hose over the relief valve in the reservoir.
    22.  
    23. Hold the other end of the tube pointed downward into the rear reservoir chamber. Turn the ignition switch ON .
    24.  
    25. If fluid flows through the tube into the reservoir, replace the relief valve. If fluid does not flow through the tube, replace the Powermaster III unit.
    26.  

    Test E - Pump Off Time Too Short
    1. Turn the ignition switch to OFF and depressurize the Powermaster III unit.
    2.  
    3. Remove the accumulator and install pressure gauge J-37118 or equivalent. Install the accumulator on the pressure gauge adapter.
    4.  
    5. Bleed the Powermaster III at the bleeder valves or use a scanner to perform ABS Solenoid Bleed and Checkout Test.
    6.  
    7. Observe the pressure gauge while turning ignition ON . The system should pressurize from 0-500 psi (0-3448 kPa) or greater almost immediately after the ignition is switched on.
    8.  
    9. If the correct pressure is not reached, the accumulator is not holding sufficient precharge and must be replaced.
    10.  
    11. Allow the system to pressurize until the pump shuts OFF. With the ignition still on, moderately apply and hold the brakes on. Measure the time between brake application and pump start-up.
    12.  
    13. If the pump OFF time is less than 50 seconds, check the accumulator precharge. If the accumulator precharge is less than 600 psi (4137 kPa), replace the accumulator. If precharge is 600 psi (4137 kPa) or greater and the pump OFF time is less than the correct value shown below, replace the Powermaster III unit.
    14.  

    Test F - External Leakage Check
    1. Depressurize the Powermaster III unit.
    2.  
    3. Clean and remove the reservoir cover and diaphragm assembly. Inspect the fluid levels.
    4.  
    5. If the front chamber level is high, drain or siphon fluid to restore the correct level.
    6.  
    7. If the rear chamber level is too high, drain or siphon fluid to restore the correct level. High level in the rear chamber may be caused by filling the reservoir without depressurizing the system.
    8.  
    9. Clean and dry the Powermaster III unit so that any leaks or seepage may be easily detected. Install the reservoir cover and diaphragm.
    10.  
    11. Turn the ignition ON and pump the brakes. Check for leaks on the Powermaster III and throughout the system, including lines, fittings and calipers.
    12.  
    13. Depressurize the Powermaster III, remove the cover and diaphragm and inspect the fluid levels. If the rear fluid level is too high, the Powermaster III must be replaced.
    14.  
    15. If the level in the front reservoir is too high:
      1. Drain or siphon the brake fluid in the front reservoir to a point below the divider wall for the left front and right front circuits.
      2.  
      3. Install the reservoir cover and diaphragm. Turn the ignition switch ON and pump the brakes several times.
      4.  
      5. Depressurize the Powermaster III. Remove the reservoir cover and the diaphragm.
      6.  
      7. Note the level of fluid in the front reservoirs. If the fluid level has risen in either front chamber, the Powermaster III must be replaced. If the fluid level has dropped or remained constant, replace the reservoir, cover and diaphragm assembly.
      8.  

    16.  

     
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