Note on Intermittents

As with virtually any electronic system, intermittent failures are difficult to accurately diagnose. The ABS trouble codes stored by the EBCM are not specifically designated as "Current" or "History" codes, as are PCM codes. These codes, however, can be helpful in diagnosing intermittent conditions.

When an intermittent condition is being diagnosed, use the ABS self-diagnostic system in the following manner to help isolate the suspect circuit:

1. Display and clear any ABS trouble codes which may be present in the EBCM.
2. Test drive the vehicle, attempting to repeat the failure condition. When available, a description of the driving circumstances under which the failure occurred can be helpful in duplicating the condition.
3. Stop the vehicle and display any ABS trouble codes which have been stored.

^ When trouble codes are stored, use the ABS Code Diagnosis Chart in this section to identify and isolate suspect circuits.
^ When no trouble codes are stored, it becomes necessary to use symptom diagnosis.

When the system malfunction is not repeated during the test drive, a good vehicle behavior description is helpful in locating a "most likely" component or circuit. The ABS Symptom Diagnosis Chart in this section is also 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). Install using terminal repair kit J 38125-A.
^ Improperly formed or damaged terminals. All connector terminals in a problem circuit should be carefully reformed to increase contact tension using terminal repair kit J 38125-A.
^ Poor terminal to wire connection. This requires removing the terminal from the connector body to inspect. Repair using terminal repair kit J 38125-A.

Most antilock brake system failures will disable antilock function for the entire ignition cycle, even when the fault clears before key-off. However, some intermittent failure conditions will allow ABS operation to resume when the fault clears before key off.

The following conditions can result in intermittent operation of the amber "ANTILOCK" indicator. Circuits involving these inputs to the EBCM should be investigated when a complaint of intermittent indicator illumination is encountered.

^ Low System Voltage
When low system voltage is detected at the EBCM, the ABS will turn on the amber "ANTILOCK" indicator until normal system voltage is achieved. Once normal voltage is seen at the EBCM, normal operation resumes.
^ Low Brake Fluid in the Pressure Modulator Valve (PMV) Assembly Reservoir
A low brake fluid condition will cause the EBCM to illuminate the amber "ANTILOCK" indicator. When the fluid level sensor again indicates an acceptable PMV reservoir fluid level, normal operation will resume.
^ Wheel Speed Sensor Circuitry
Additionally, any condition which results in interruption of power to the EBCM or hydraulic unit may cause the indicator to illuminate intermittently. These circuits include the main relay, pump motor relay and fuses, and related wiring.