ABS Diagnosis and Testing

ABS DIAGNOSIS AND TESTING
The ABS is an integral part of the braking system and as such must be serviced with care. Servicing of the ABS must be performed in a planned and orderly fashion to assure that problems are addressed and resolved properly. The procedures and information in this section are provided to assist in servicing the ABS. The general procedure when servicing the ABS is described as follows:

1. Record the driver's statement describing any symptoms of problems with the vehicle's braking system.
2. Compare the driver's symptoms to those listed in the charts that are a part of the Diagnosis by Symptom. Knowing what the probable source of the symptom is will be helpful when doing the remaining diagnosis and testing. Symptom Related Diagnostic Procedures
3. Before going further with the diagnosis, it is critical to know whether or not the ABS warning light is functioning properly.
4. If the driver's statement is vague, or lacking in detail, it may be necessary to drive the vehicle to gain additional information. Be aware that the ABS Control Unit may detect new problems and store additional diagnostic trouble codes in its memory during this test drive. Test Drive
5. Record any four-digit diagnostic trouble codes that are stored.
Displaying & Reading Trouble Codes
6. If the source of the problem is obvious at this point, particularly if that source is believed to be an individual component, the ABS Component Quick Check Table may be helpful. This table can also be referred to for specifications when other procedures require you to evaluate a component. ABS Component Quick Check
7. Each of the 16 component tests provides a test procedure for a specific component, its associated wiring, and the corresponding circuitry in the ABS Control Unit. These individual tests are referred to by the symptom diagnosis charts and the retrieval of diagnostic trouble codes. Do only those component tests, or portions thereof, that you art directed to do.
8. In the event that a problem has not been resolved after completion of the component tests, it should be assumed that symptoms of the problem are intermittent. The exact source must be pinpointed. Intermittent Symptom Diagnosis Procedure
9. Perform a final Drive Test before returning the vehicle to regular service. Determine that the ABS works properly during the Low Speed ABS Stop, and that it does not activate during the Non-ABS Stop. Also, be alert to the presence of any new symptoms or uncorrected symptoms. Verify that additional diagnostic trouble codes do not exist. Test Drive