LS 2006

Diagnosis & Testing


The Anti-lock-Brake System (ABS) module receives wheel speed readings from each wheel speed sensor and processes this information to determine if an ABS event is necessary. The wheel speed sensor electrically senses each tooth of the wheel speed sensor ring as it passes through the wheel speed sensor magnetic field.

The ABS module continuously monitors and compares the rotational speed of each wheel and, when it detects an impending wheel lock, modulates brake pressure to the appropriate brake caliper. This is accomplished by triggering the Hydraulic Control Unit (HCU) to open and close the appropriate solenoid valves. Once the affected wheel returns to normal speed, the ABS module returns the solenoid valves to their normal position, and normal (base) braking resumes.

The ABS module is self-monitoring. When the ignition switch is turned to the RUN position, the ABS module will do a preliminary electrical check, and at approximately 20 km/h (12 mph) the pump motor is turned on for approximately one half-second. Any malfunction of the ABS will cause the ABS to shut off and the yellow anti-lock brake warning indicator to illuminate. Normal power assisted braking, however, remains.

The ABS module must be configured upon replacement.

  1. Before servicing the vehicle, refer to the Precautions section.
  3. Visually inspect for obvious signs of mechanical and electrical damage. If the fault is not visually evident, connect the diagnostic tool to the Data Link Connector (DLC) located beneath the instrument panel and select the vehicle to be tested from the diagnostic tool menu. If the diagnostic tool does not communicate with the vehicle:

    check that the program card is correctly installed.
    check the connections to the vehicle.
    check the ignition switch position.

  5. If the diagnostic tool still does not communicate with the vehicle, refer to the diagnostic tool manual.
  7. Carry out the DATA LINK DIAGNOSTIC TEST. If the diagnostic tool responds with:

    SYSTEM PASSED, retrieve and record the continuous Diagnostic Trouble Codes (DTCs), erase the continuous DTCs and carry out the self-test diagnostics for the ABS module.

  9. If the DTCs retrieved are related to the concern, go to the Anti-Lock Brake System (ABS) Module Diagnostic Trouble Code (DTC) below to continue diagnostics:

    B1342: ECU is Defective
    B1485: Brake Pedal Input Circuit Battery Short
    B1676: Battery Pack Voltage Out of Range
    B2477: Module Configuration Failure
    C1095: Hydraulic Pump Motor Circuit Failure
    C1145: Speed Wheel Sensor RF Input Circuit Failure
    C1155: Speed Wheel Sensor LF Input Circuit Failure
    C1165: Speed Wheel Sensor RR Input Circuit Failure
    C1175: Speed Wheel Sensor LR Input Circuit Failure
    C1233: Speed Wheel LF Input Signal Missing
    C1234: Speed Wheel RF Input Signal Missing
    C1235: Speed Wheel RR Input Signal Missing
    C1236: Speed Wheel LR Input Signal Missing
    C1805: Mismatched PCM and/or ABS Module
    U1009: SCP (J1850) Invalid or Missing Data for Engine Torque
    U1027: SCP (J1850) Invalid or Missing Data for Engine RPM
    U1262: SCP (J1850) Communication Bus Fault