Antilock Brake System for Early Subarus:
The Antilock Brake System (ABS) warning lamp illuminates on the instrument panel to indicate a malfunction of the system. The ECU cannot identify mechanical problems, only electrical problems. A trouble code is flashed by the LED located on the ECU to indicate problems with the following:
• magnetic valves
• speed sensors
• valve relay
• plunger pump motor relay
• plunger pump motor
To access the trouble codes, drive the vehicle at a speed greater than 25 MPH for more than one minute. Stop the vehicle with the engine at idle, the trouble code flashes on the LED.
The ECU only displays one trouble code, the lowest numbered code. Correct the fault indicated by the trouble code and recheck ECU for another code. Repeat self-diagnostic procedure listed above, and the next highest code will be displayed. Refer to the appropriate model year service manual for the trouble codes and corrective actions.
While the Antilock Brake System (ABS) ECU is in the fault mode, the ABS will go to fail-safe and remain passive under all braking conditions. The brake system will function as a conventional power assisted system without ABS.