Initial Inspection and Diagnostic Overview

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

Serial data is transmitted by the EBCM through terminal "2" (ABS w/o VES) or "1" (ABS w/VES). The EBCM is supplied switched ignition voltage through terminal "14", battery voltage through terminal "15" and switched battery voltage through terminal "A". The EBCM ground is provided through terminal "B".

Diagnostic System Check (Part 1 0f 4):

Fig. 395 Diagnostic Circuit Check (Part 2 Of 4):

Fig. 395 Diagnostic Circuit Check (Part 3 Of 4):

Fig. 395 Diagnostic Circuit Check (Part 4 Of 4):

Diagnostic System Check:

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 link malfunction.
3. Checks for proper Tech 1 connection to DLC.
4. Checks for open Fuse 11.
5. Checks for an open Fuse 4
6. Checks for high resistance in the EBCM ground circuit.
9. 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 B+ feed circuitry.
11. Checks for a 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 the short to ground is not due to physical damage of the circuitry.
16. Checks for proper battery voltage at the EBCM.
17. Checks for high resistance in the B+ feed circuitry.
18. Checks for high resistance in the switched ignition circuitry.
19. Ensures that the 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.