Diagnostic Circuit Check: Notes

Diagnostic circuit check is an organized approach in identifying a problem created by an anti-lock brake system 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 a complaint. Understanding the chart and using it correctly will reduce diagnostic time and prevent unnecessary replacement of good parts.

1. Indicates if EBCM is transmitting data.
2. Checks for serial data line malfunction.
3. Checks for proper Tech 1 connection to DLC.
4. Checks for an open TAIL DOME fuse.
5. Checks for an open REAR DEF fuse.
6. Checks for high resistance in EBCM ground circuit
7. Checks for current DTCs.
8. Checks for proper ABS warning light operation.
9. Checks for history DTCs.
10. Checks for short to ground in battery feed circuit.
11. Checks for short to ground in EBCM.
12. Ensures short to ground is not due to physical damage of circuitry.
13. Checks for short to ground in switched ignition circuit.
14. Isolates short to ground to either the circuitry or the EBCM.
15. Ensures short to ground is not due to physical damage of circuitry.
16. Checks for open in White wire between EBCM and TAIL DOME fuse.
17. Checks for high resistance in battery feed circuit.
18. Checks for high resistance in switched ignition circuit.
19. Ensures malfunction is not due to poor terminal contact.
20. Checks for high resistance in switched ignition circuit between REAR DEF fuse and the EBCM.