ABS System Self-Diagnostics

SELF TEST
The microprocessor in the Controller Antilock Brake (CAB) has both a self test feature and a memory. The self test feature occurs every time the ignition key is turned to the START or RUN positions and continues as long as the ignition is in the RUN position. During the self test, the microprocessor monitors and processes signals generated by the systems inputs and outputs. It also performs a bulb check when the ignition key is first turned to START or RUN which turns on the brake warning lamp (red) and the ABS warning lamp (amber). If the self test does not identify any malfunctions, both lamps will illuminate for a few seconds and then go out.

FAULT DETECTION
If a system fault is detected, the ABS warning lamp and the brake warning lamp are illuminated. A Diagnostic Trouble Code (DTC) is also stored in the microprocessor's memory. The DTC remains in memory even after the ignition key is turned to OFF with the exception of codes 9 and 11 which are erased anytime the ignition key is turned to OFF. The memory has the capability to store only one DTC at any given time. The problem that caused the DTC must be repaired and the DTC erased before another code will appear (if any).

SYSTEM MALFUNCTION
If a system malfunction should occur, DO NOT immediately replace the CAB. A blown system fuse, poor ground, or loss of feed voltage will cause system faults similar to a CAB failure. Never replace the CAB unless the diagnostic procedure identifies a CAB replacement is necessary.