Initial Inspection and Diagnostic Overview

DIAGNOSTIC SYSTEM CHECK

Diagnostic System Check (Part 1 Of 4).:

Diagnostic System Check (Part 2 Of 4).:

Diagnostic System Check (Part 3 Of 4).:

Diagnostic System Check (Part 4 Of 4).:

Diagnostic System Check:

SYSTEM DESCRIPTION:
The diagnostic system check is an organized approach to identifying 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 transmitted/received by the EBCM/EBTCM through terminal "12". The EBCM/EBTCM is supplied switched ignition voltage through terminal "4" and battery voltage through terminal "13". The EBCM/EBTCM ground is provided through terminal "D".

CHART TEST DESCRIPTION:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Indicates if EBCM/EBTCM is transmitting data.
2. Checks for a serial data link malfunction.
3. Checks for proper Tech 1 connection to DLC.
4. Checks for open ERLS Fuse.
5. Checks for an open INT LPS Fuse.
6. Checks for high resistance in the EBCM/EBTCM ground circuit.
7. Checks for current DTCs.
8. Checks for proper ABS indicator lamp operation.
9. Checks for history DTCs.
10. Checks for possible short to ground in the B+ feed circuitry.
11. Checks for a possible short to ground in the switched ignition circuit.
12. Ensures short to ground is not due to physical damage of the circuitry.
13. Checks for possible short to ground in the battery feed circuitry.
14. Isolates the short to ground to either the wiring circuitry or the EBCM/EBTCM.
15. Ensures the short to ground is not due to physical damage of the circuitry.
16. Checks for proper battery feed voltage at the EBCM/EBTCM.
17. Checks for proper ignition feed voltage at the EBCM/EBTCM.
18. Checks for high resistance in the battery feed circuit and the switched ignition feed circuit.
19. Ensures malfunction is not due to poor terminal contact.
20. Checks for an open circuit in the battery feed circuit between the fuse block and the EBCM/EBTCM.
21. Checks for an open circuit in the switched ignition feed circuit between the fuse block and the EBCM/EBTCM.
22. Isolates the high resistance circuit to either the battery feed circuit or the switched ignition feed circuit.
23. Isolates the high resistance in the battery feed circuit between the fuse block or the EBCM/EBTCM circuitry.
24. Isolates the high resistance in the ignition feed circuit between the fuse block or the EBCM/EBTCM circuitry.

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