Inspection and Verification
Inspection and VerificationNOTE: Ensure the integrity of all connectors and their associated harnesses.
1. Verify the customer concern by applying brakes under different conditions.
2. Visually inspect for obvious signs of mechanical and electrical damage.
3. If the fault is not visually evident, verify the symptom and proceed to Self Test.
System Pre-Check
NOTE: Carry out this procedure first. Failure to do so may result in incorrect diagnosis of the problem and improper replacement of components.
The system pre-check screens a vehicle for relatively simple diagnostic repairs, such as loose connectors, blown fuses, etc. However, the system pre-check also prepares the vehicle for further diagnostics. In addition, warning indicator concerns are diagnosed in this system pre-check.
The RABS module uses the yellow ABS warning indicator and under some conditions the red brake warning indicator to alert the driver to a system malfunction. Both lights must be working properly to assist in diagnosis. The steps below must be followed prior to beginning the RABS diagnostic procedure.
Vehicle Setup
WARNING: Place blocks behind the rear wheels and in front of the front wheels to prevent the vehicle from moving while the system pre-check is being done.
For 4WD vehicles, shift into 2WD. Drive the vehicle to a level area, and place the shift lever in PARK for automatic transmissions and NEUTRAL for manual transmissions. Turn the ignition off, set the parking brake, and turn on the running lamps. Place blocks behind the rear wheels and in front of the front wheels. Release the parking brake.
Warning Indicator Lamp
The red BRAKE warning indicator is constantly monitored by the anti-lock brake control module. If the red BRAKE warning indicator illuminates, the anti-lock brake control module will disable the RABS system and turn on the yellow ABS warning indicator. For this reason, diagnosing and resolving any base brake concerns illuminating the red BRAKE warning indicator will, in most cases, resolve a perceived RABS concern.
Red BRAKE Warning Indicator Self-Check
The red BRAKE warning indicator is used to indicate a low fluid level condition or parking brake applied condition. To check this light, insert the key in the ignition switch and turn it to the START position. The warning indicator should illuminate in this position. If the red brake warning indicator fails to illuminate, go to the Symptom Chart.
Allow the key to spring back from the START position to the RUN position. At this time, the red BRAKE warning indicator should turn off. If it does not turn off, recheck the parking brake switch to make sure that it is fully disengaged. In the event that the red BRAKE warning indicator remains on, go to the Symptom Chart. Symptom Related Diagnostic Procedures
Yellow ABS Warning Indicator
The yellow ABS warning indicator is used to indicate a malfunction and a deactivation of the RABS system. To check this indicator, first follow the procedure for Red BRAKE Warning Indicator Self-Check, and allow the key to spring back from the START position to the RUN position. The yellow ABS warning indicator should prove-out by illuminating for approximately 1-2 seconds and then turning off.
If the ABS indicator light remains on after prove-out, the module has detected a currently existing fault and has stored a DTC in memory. This is referred to as a hard fault. A soft fault is one that occurred, caused the indicator to come on and then went away. These are an intermittent type of fault and will not cause a DTC to be stored in the module's memory. Continue to Diagnostic Trouble Codes, Retrieving for obtaining diagnostic trouble codes. If the yellow ABS warning indicator fails to illuminate, go to the Symptom Chart. Symptom Related Diagnostic Procedures
Diagnostic Trouble Codes (DTCs), Retrieving
CAUTION: Care must be taken to connect only the black/orange stripe wire to ground. Connecting the mating connector wire to ground will result in a blown fuse.
Verify the ignition switch is in the RUN position (engine does not need to be running). Next, locate the black RABS, diagnostic connector C207. The diagnostic connector C207 has two mating halves, one of which has a black/orange (BK/OG) wire connected to it. Disconnect the two halves.
Attach one end of a jumper wire to the black/orange (BK/OG) wire side of the diagnostic connector C207. Ground the opposite end of the jumper wire by connecting it to a ground until the ABS light begins to flash. Grounding this wire should start the yellow ABS warning indicator flashing. If grounding this wire does not start the yellow ABS warning indicator flashing, go to the Symptom Chart. Symptom Related Diagnostic Procedures
The code consists of a number of short flashes and ends with a long flash. Count the short flashes and include the following long flash in the count to obtain the code number. For example, three short flashes followed by one long flash indicates diagnostic trouble code 4. The code will continue to repeat itself until the key is turned off. It is recommended that the code be verified by reading it several times. This code will be used later for system repair instructions. It should be written down for future use. A diagnostic trouble code 16 is obtained when the anti-lock brake control module detects normal system operation.
Diagnostic Trouble Codes (DTCs), Erasing
The last step of the system pre-check always includes clearing the keep alive memory KAM). Turn off the ignition while the diagnostic connector C207 halves are separated as described in Diagnostic Trouble Codes, Retrieving. The diagnostic connector C207 should be re-assembled to provide KAM power to the anti-lock brake control module.
If a valid code has been obtained, go to the Symptom Chart. Symptom Related Diagnostic Procedures