Diagnostic System Check - ABS

Diagnostic System Check:

System Description:
The diagnostic system check is an organized approach to identifying a problem created by an Antilock Brake System (ABS) malfunction. It must be the starting point for any ABS complaint diagnosis because it directs the service technician to the next logical step in diagnosing the complaint.

Serial data is exchanged by the EBCM through connector "C1," terminal "E11." The EBCM is supplied switched ignition voltage through connector "C1," terminal "F11," battery voltage through connector "C1," terminal "F10" and switched battery voltage through connector "C2," terminal "D." The EBCM ground is provided through connector "C2," terminal "E."

Chart Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Indicates if EBCM is transmitting data.
2. Checks for a serial data line malfunction.
3. Checks for proper Tech 1 connection to DLC.
4. Checks for an open ABS-ECU fuse.
5. Checks for an open ABS fuse.
6. Checks for high resistance in the EBCM ground circuit.
7. Checks for current DTCs.
8. Checks for proper "ABS" warning lamp operation.
9. Checks for history DTCs.
10. Checks for possible short to ground in the battery feed circuitry.
11. Checks for possible short to ground in the EBCM.
12. Ensures short to ground is not due to physical damage of the circuitry.
13. Checks for possible short to ground in the switched ignition circuitry.
14. Isolates the short to ground to either the circuitry or the EBCM.
15. Ensures short to ground is not due to physical damage of the circuitry.
16. Checks for an open in CKT 1140.
17. Checks for high resistance in battery feed circuitry.
18. Checks for high resistance in the switched ignition circuitry.
19. Ensures malfunction is not due to poor terminal contact.
20. Checks for high resistance in the switched ignition circuit between the fuse block and the EBCM.

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 the ABS ground connection is good and that there is no excessive resistance in any of the power supply circuits.