Antilock Braking System (ABS)

Chart A (Part 1 Of 2):

Chart A (Part 2 Of 2):

Chart A Wiring Schematic:

CIRCUIT DESCRIPTION
When the ignition is first turned to "RUN," the Electronic Brake Control Module (EBCM) goes through a self-check lasting 2-4 seconds. During this test the EBCM grounds terminal 34, energizing the main relay. Once the self-check is completed the main relay remains energized. This delivers battery voltage to both the EBCM and the Pressure Modulator Valve (PMV) assembly during vehicle operation. The constant voltage supply allows the vehicle to enter ABS mode without delay. The main relay is de-energized whenever the amber "ANTILOCK" indicator lights, causing the ABS system to shut down.

Code 45 sets when the ignition switch is at "RUN" and battery voltage is neither detected at the PMV assembly nor EBCM terminal 20, 3 and/or 33. Code 45 also sets when the EBCM detects an open or a short to ground in the LH inlet valve circuit.

Possible Causes
^ Open in circuit 650, 855, 858, 1077 or 1443.
^ Short to ground in circuit 858, 1077 or 1443.
^ Main relay fails "open."