GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2008 🢒 Isuzu H-Series 🢒 Brakes 🢒 Air Antilock Brake System 🢒 Air ABS Indicator Always On

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The electronic brake control module (EBCM) sends a central area network (CAN) serial data message to the serial data gateway (SDG) module. The SDG module converts the CAN message to a class 2 serial data message and sends the message to the instrument panel cluster (IPC). The IPC interprets the class 2 message from the SDG module and commands the Antilock Brake System (ABS) indicator ON or OFF.

Diagnostic Aids
    •  If your vehicle is showing the brake or low air warning light is on and you either are not equipped with ABS or do not have an ABS warning light ON then there is a problem with the regular brake system.
    •  Replace the Instrument Panel Cluster (IPC) if the ABS indicator intermittently fails to operate during the bulb check.
    •  The malfunction must be present during diagnosis in order to prevent unnecessary parts replacement. Always begin diagnosis with the Diagnostic System Check refer to Diagnostic System Check - Vehicle.

Reference Information

Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for EBCM and IPC

Circuit/System Verification

With the scan tool, select instrument panel special functions Lamp Test. Command the instrument panel warning lamp OFF. The ABS Warning light should turn OFF with the command.

Circuit/System Testing

Important: Diagnose all vehicle DTCs before using this diagnostic.

With the scan tool, select instrument panel special functions Lamp Test. Command the instrument panel warning lamps OFF.

⇒If the ABS warning lamp does not turn OFF, replace the IPC.
⇒If the ABS lamp turns OFF and there are no DTCs stored in any vehicle systems, replace the EBCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for EBCM or IPC replacement, setup, and programming

Repair Verification
  1. Turn OFF the ignition for 5 seconds.
  2. Turn ON the ignition, while observing the ABS Warning Light Indicator.
  3. The ABS Warning Light Indicator should light for 2 seconds then turn off.
    4. ⇒If the ABS indicator does not light, recheck the circuit/system testing.