Diagnostic System Check

EBCM/ABS Schematic:

GENERAL INFORMATION
The Diagnostic System Check is an organized approach to identifying 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.

CIRCUIT DESCRIPTION
Serial data is transmitted/received by the Electronic Brake Control Module (EBCM) through connector C1 terminal C5. The EBCM is supplied switched ignition voltage through connector C1 terminal D9 and battery feed voltage through connector C1 terminal D8. The EBCM ground is provided through connector C2 terminal B.

DIAGNOSTIC AIDS
Items To Inspect
The following list contains items that need to be inspected when diagnosing this system:
^ Open REAR DEFG fuse.
^ Open TAIL DOME fuse.
^ Clean, tight G105.

Resistance And EBCM Communication
Excessive resistance in the following circuits will not allow communication with the EBCM:
^ 1L08 - Battery feed.
^ 1Y03 - Switched ignition.
^ 9V01/G105 - Ground.
^ 3H01 - Serial data line.

NOTE: If communication with the EBCM is not possible with a scan tool, ensure that the above circuits are in good condition and that there is no excessive resistance. Also check EBCM connectors C1 and C2 for poor connector terminal contact.

ABS Diagnostic System Check (Part 1 Of 5):

ABS Diagnostic System Check (Part 2 Of 5):

ABS Diagnostic System Check (Part 3 Of 5):

ABS Diagnostic System Check (Part 4 Of 5):

ABS Diagnostic System Check (Part 5 Of 5):

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
[1] Performs two drive cycles. The EBCM checks the motors and solenoids during initialization.
[3] Checks for any Diagnostic Trouble Code (DTC)s that may have set in the past 100 drive cycles.
[4] Checks for a faulty or improperly set scan tool.
[5] Checks for an open in the serial data line circuit between the EBCM and DLC (CKT 3H01).
[6] The amber ABS indicator could either flash or not turn ON at all.
[8] A flashing amber ABS indicator could indicate a degrade of base brake system.
[12] Checks for history DTCs stored in the EBCM.
[14] Checks for current DTCs.
[18] Checks for a poor ground to the EBCM (G105).
[19] Checks for a short to ground in CKT 1Y03.
[21] Checks for a faulty EBCM causing to open the REAR DEFG fuse.
[22] Checks for a short to ground in CKT 1L08.
[24] Checks for a faulty EBCM causing to open the TAIL DOME fuse.
[25] Checks for an open in CKT 1L08.
[26] Checks for an open in CKT 1Y03.