Diagnostic System Check

Four Wheel ABS Schematic:

SYSTEM DESCRIPTION
The diagnostic system check is an organized approach to identifying a problem created by 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 exchanged by the Electronic Brake Control Module (EBCM) through connector C1, terminal F. The EBCM is supplied switched ignition voltage through connector C1, terminal A, and ground is provided through connector C1, terminal J.

Diagnostic System Check (Part 1 Of 2):

Diagnostic System Check (Part 2 Of 2):

CHART TEST DESCRIPTION
Numbers below refer to numbers on the diagnostic chart.
[1] Indicates if the EBCM is transmitting data.
[2] Checks for a serial data line malfunction.
[3] Checks for proper scan tool connection to Diagnostic Link Connector (DLC).
[4] Checks for open BRAKE fuse.
[6] Checks for high resistance in the EBCM ground circuit.
[7] Checks for current Diagnostic Trouble Codes (DTC)s.
[8] Checks for proper ANTILOCK indicator lamp operation.
[9] Checks for history DTCs.
[12] Checks for possible short to ground in the battery feed circuitry.
[13] Checks for possible short to ground in the EBCM.
[14] Ensures short to ground is not due to physical damage of the circuitry.
[15] Checks for an open in circuit 441.
[16] Ensures malfunction is not due to poor terminal contact.

4WAL Connector Face Views:

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.