Antilock Brakes / Traction Control Systems: Testing and Inspection

Fig. 2 Rear wheel Anti-Lock (RWAL) self-diagnostic connector location:

Fig. 3 Rear wheel anti-lock flashing pattern of a trouble code 3.:

The RWAL system utilizes 13 self-diagnostic codes to isolate a detected system failure. Momentarily grounding the RWAL diagnostic lead, Fig. 2, with the rear anti-lock lamp ``On'' will cause the lamp to flash out a diagnosis code if a system shutdown has been detected and is stored in the Electronic Control Module (ECM).
Reading RWAL Trouble Codes
Count the number of short flashes starting from the long flash as a count Fig. 3. Sometimes the first count sequence is short because the flashout started with the count already in progress. Subsequent counts will be accurate. If there is more than one system failure, only the first recognized diagnostic code will be retained in memory and flashed. If a diagnostic code is obtained, go to the flashout code chart, refer to DIAGNOSTIC CHARTS.

Trouble code diagnosis

Some diagnostic procedures require that the ignition switch remain on for extended periods of time while tests are performed. Low battery voltage may result, causing erroneous voltage readings. If vehicle system voltage becomes low, it is advisable to connect a battery charger and apply a slow charge while testing.