Fault finding

FAULT FINDING

Anti-lock Brake System (ABS) Indicator Light

70M 0115

A   ABS indicator light

Temporary Driving Conditions:

1. The ABS indicator light comes on and the ABS control unit memorizes the diagnostic trouble code (DTC) under certain conditions.
2. If you receive a customers report that the ABS indicator light sometimes comes on, check the fault code in the ECU memory. Then use microcheck to determine the fault. Do not use microcheck before checking the fault code as this disconnects the ECU from the battery and will cause any fault codes to be lost.

• The tyre(s) adhesion is lost due to excessive cornering speed.
  DTC: 5, 5–4, 5–8.
• The vehicle loses traction when attempting to move from rest on a muddy, snowy, or sandy road.
  DTC: 4–1, 4–2, 4–4, 4–8
• When the parking brake is applied for more than 30 seconds while the vehicle is being driven.
  DTC: 2–1
• The vehicle is driven on an extremely rough road.

The ABS is OK, if the ABS indicator light goes off after the engine is restarted.

3. If you receive a customer's report that the ABS indicator light sometimes comes on, check the system using the ALB checker to confirm whether there is any trouble in the system.
4. The ABS indicator light will come on and the ABS control unit will memorize a DTC when there is insufficient battery voltage to the ABS control unit. An example would be when the battery is so weak that the car must be jump-started. After the battery is sufficiently recharged, the ABS indicator light will work normally after the engine is stopped and restarted.

However, after recharging the battery, the DTC must be cleared from the ABS control unit's memory by disconnecting the ABS B2 (15 A) fuse in the under-hood ABS fuse/relay box for at least three seconds.

ABS Indicator Light Circuit:

CAUTION: Use only the digital multimeter to check the system.

1. The ABS indicator light does not go on when the ignition switch is turned on.

Check the following items. If they are operational, check the ABS control unit connectors. If not loose or disconnected, substitute a known-good ABS control unit and recheck.

• Blown ABS indicator light bulb.
• Open circuit in YEL wire between the No. 8 TURN SIGNALS, BACK-UP LIGHTS (10 A) fuse in the under-dash fuse/relay box and gauge assembly.
• Open circuit in BLU/RED wire between the gauge assembly and ABS control unit.
• Poor ground connection between the ABS control unit and the body.