Diagnostic System Check

Part 1 Of 2:

Part 2 Of 2:

System Description
The diagnostic system check is an organized approach to identifying an Antilock Brake System (ABS) malfunction. The diagnostic system check must be the starting point for any ABS complaint diagnosis. The diagnostic system check directs the service technician to the next logical step in diagnosing the complaint. Refer to the table.
Diagnostic serial data is transmitted/received by the EBCM through connector C1, terminal G. The EBCM is supplied battery voltage through connector C3, terminal A and switched ignition voltage through connector C1, terminal A. Grounds are provided through connectors C1, terminal J. and C3 terminal B.

Diagnostic Aids
Excessive resistance in the ground or power supply circuits will not allow communication with the EBCM. If communication with the EBCM is not possible, ensure that the ABS ground connection is good and that there is no excessive resistance in any of the power supply circuits.

Test Description
The numbers below refer to the steps in the diagnostic table:
3. This step checks for normal ABS indicator lamp operation.
4. This step checks for ignition voltage at the EBCM.
5. This step checks for high resistance in the ground circuit.
9. This step checks for high resistance in the ignition voltage circuit.
10. This step checks for a short to ground in the ignition voltage circuit.
11. This step decides between ABS indicator lamp on always, or off always as the symptom. This step decides between a short to ground in the 10-way EBCM harness/connector, or an internal EBCM fault.
18. Using the scan tool, this step attempts to show that the EBCM can control turning the ABS indicator lamp off, but the instrument cluster is not responding.
20. Using the scan tool, this step attempts to show that the EBCM can control turning the ABS indicator lamp on, but the instrument cluster is not responding.