Diagnostic System Check - ABS

Diagnostic System Check (Part 1 Of 5):

Diagnostic System Check (Part 2 Of 5):

Diagnostic System Check (Part 3 Of 5):

Diagnostic System Check (Part 4 Of 5):

Diagnostic System Check (Part 5 Of 5):

ABS Schematic:

Circuit 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 Electronic Brake Control Module (EBCM) through connector C1 terminal C5. The EBCM is supplied switched ignition voltage through connector C1 terminal D9 and battery feed voltage through connector C1 terminal B12. The EBCM ground is provided through connector C2 terminal D.

Diagnostic Aids
The following list contains items that need to be inspected when diagnosing this system:
- Open GIG-RADIO fuse.
- Open TAIL DOME fuse.
- Clean, tight G103.

Excessive resistance in the following circuits will not allow communication with the EBCM:
- 140 - Battery feed.
- 350A/B/C/D - Switched ignition.
- 150A/G103 - Ground.
- 461A/B/C - Serial data line.

If communication with the EBCM is not possible with a scan tool, ensure these circuits are in good condition and that there is no excessive resistance. Also check EBCM connectors C1 and C2 for poor connector terminal contact.



Test Description

NOTE:The numbers below refer to step numbers on the diagnostic table.
1. Performs two drive cycles. The EBCM checks the motors and solenoids during initialization.
3. Checks for any DTCs that may have set in the past 100 drive cycles.
4. Checks for a faulty or improperly set scan tool.
5. Checks for an open in the serial data line circuit between the EBCM and DLC (CKT 461A/B/C).
6. The amber ABS indicator could either flash or not turn ON at all.
8. A flashing amber ABS indicator could indicate a degrade of base brake system.
12. Checks for history DTCs stored in the EBCM.
14. Checks for current DTCs.
18. Checks for a poor ground to the EBCM (G103).
19. Checks for a short to ground in CKT 350A/B/C/D
21. Checks for a faulty EBCM causing to open the GIG-RADIO fuse.
22. Checks for a short to ground in CKT 140.
24. Checks for a faulty EBCM causing to open the DOME fuse.
25. Checks for an open in CKT 140.
26. Checks for an open in CKT 350A/B/C/D.