Note on Intermittents

As with virtually any electronic system, intermittent failures in the Anti-Lock Brake system may be difficult to accurately diagnose. If an intermittent condition is being diagnosed, the ABS self-diagnostic system can be used in the following manner to help isolate the suspect circuit:

^ First, display and clear any ABS trouble codes which may be present in the EBCM.
^ Then test drive the vehicle, attempting to repeat the failure condition. A description of the driving circumstances under which the failure occurs, if available, can be helpful in duplicating the condition.
^ After duplicating the condition, stop the vehicle and display any ABS trouble codes which may have been stored.
^ If no trouble codes were stored, it may become necessary to use symptom diagnosis.

If the system malfunction is not repeated during the test drive, a good description of vehicle behavior may be helpful in locating a 'most likely' component or circuit. The symptom diagnosis chart may also be useful in isolating the failure.

Most intermittent problems are caused by faulty electrical connections or wiring. When an intermittent failure is encountered, check suspect circuits for:

^ Poor mating of connector halves or terminals not fully seated in the connector body (backed out).
^ Improperly formed or damaged terminals. All connector terminals in a problem circuit should be carefully reformed to increase contact tension.
^ Poor terminal to wire connection. This requires removing the terminal from the connector body to inspect.
^ Wheel speed sensor cables not attached in retainers or routed too close to spark plug wires.

Most failures of the Anti-Lock Brake System will disable anti~lock function for the entire ignition cycle, even if the fault clears before key-off. There are a few failure conditions, however, which will allow ABS operation to resume during the ignition cycle in which a failure occurred if the failure conditions are no longer present.

Low system voltage may result in intermittent operation of the ANTI-LOCK light. All other failures will cause the warning light to remain on until the ignition switch is turned off and then back on. Circuits involving these inputs to the EBCM should be investigated if a complaint of intermittent warning system operation is encountered.

^ Low System Voltage
If low system voltage is detected at the EBCM, the ABS will turn on the ANTI-LOCK light until normal system voltage is achieved. Once normal voltage is detected at the EBCM, normal operation resumes.