When the ECU detects a fault, the ANTI-LOCK warning lamp on the dash will be light. The ECU will perform a self-diagnosis to identify the problem. When a vehicle is presented with a apparent ABS problem, it must be test driven above 19 mph (30 km/h) for at least 1 minute; this allows the ECU time to test the system and store a diagnostic code if possible.
The stored code will be displayed by the flashing of the LED on the electronic control unit. The display begins when the vehicle comes to a full stop after the self-diagnosis process. The engine must be running for the code to display. The stored code will repeat after a 5-10 second pause.
Both the ANTI-LOCK warning lamp and the LED will remain light after repairs are made. The vehicle must be driven above 19 mph for at least 1 minute. If the ECU performs the self-diagnosis and finds no fault, the lamps will extinguish.
After the visual checks of the complete brake system, (normal brake system problems corrected) and detailed description is obtained of the problem, proceed as follows:
- Refer to the Symptom Chart to determine diagnostic path.
- Perform preliminary and visual checks.
- Put the vehicle through the self-diagnosis cycle and record any fault code. Refer to the proper Diagnostic Chart for the code.
- If no code is stored, refer to other diagnostic procedures listed in the Symptom Chart.
- The diagnostic Charts direct the testing of components, connectors and ground circuits. Once the problem is identified, repair or replace items as needed.
- Put the vehicle through another self-diagnosis cycle, checking for both stored codes and proper ABS performance.
Certain driver induced faults, such as not releasing the parking brake fully, excessive wheel spin on low traction surfaces, high speed acceleration or riding the brake pedal may set fault codes and trigger a warning lamp. These induced faults are not system failures but examples of vehicle performance outside the parameters of the control unit.