Diagnostic System Check: Notes

Diagnostic system check is an organized approach to identifying a problem created by an Anti-Lock Brake System (ABS) malfunction. This should be the starting point for any ABS diagnosis because it directs technician to next logical step in diagnosing a complaint.

Serial data is transmitted through EBCM terminal No. 2. Switched ignition voltage is supplied through EBCM terminal No. 14, battery voltage through EBCM terminal No. 15 and switched battery voltage through EBCM terminal "A". Ground is through EBCM terminal "B".

1. Indicates if EBCM is transmitting data.
2. Checks for serial data line malfunction.
3. Checks for proper connection of Tech 1 scan tester to DLC.
4. Checks for open A/C-heater fuse.
5. Checks for open in CLSTR fuse.
6. Checks high resistance in EBCM battery feed circuit.
7. Checks for current codes.
8. Checks for proper ABS warning light operation.
9. Checks for history codes.
10. Checks for possible short to ground in switched ignition circuit.
11. Isolates short to ground to either circuitry or EBCM.
12. Ensures short to ground is not due to physical damage of circuit.
13. Checks for possible short to ground in battery feed circuit.
14. Isolates short to ground to EBCM or EBCM circuit.
15. Ensures short to ground is not due to physical damage of circuit.
16. Checks for proper battery feed voltage at EBCM.
17. Checks for proper ignition feed voltage at EBCM.
18. Checks for high resistance in battery feed circuit and switch ignition feed circuit.
19. Ensures malfunction is not due to poor terminal contact.
20. Checks for open circuit in battery feed circuit between fuse block and EBCM.
21. Checks for open circuit in switched ignition feed circuit between fuse block and EBCM.
22. Isolates high resistance circuit to either the battery feed circuit or the switched ignition feed circuit.
23. Isolates high resistance in battery feed circuit between fuse block and EBCM.
24. Isolates high resistance in ignition feed circuit between fuse block and EBCM.