Inspection Procedure 3

INSPECTION PROCEDURE 3, The ABS warning light remains illuminated after the engine is started








NOTE: This diagnosis procedure is limited to cases where communication with the scan tool is possible (ABS-ECU power supply is normal) and no diagnostic trouble code outputs.

CIRCUIT OPERATION
- The ABS-ECU controls the illumination of the ABS warning light by turning the power transistor in the control unit ON and OFF
- The ABS-ECU illuminates the ABS warning light on start-up. It turns the light off after 3 seconds when the ABS-ECU completes the self-check.

TECHNICAL DESCRIPTION (COMMENT)
The cause is probably the ABS-ECU and hydraulic unit assembly malfunction.

TROUBLESHOOTING HINTS (The most likely causes for this condition:)
- Damaged wiring harness
- Malfunction of the hydraulic unit (integrated with ABS-ECU)

DIAGNOSIS
Required Special Tool:
- MB991223: Harness Set





STEP 1. Check the ABS warning light circuit at ABS-ECU connector A-02.
1. Disconnect ABS-ECU connector A-02.
2. Turn the ignition switch to the "ON" position.
Q: Is the ABS warning light Illuminate?
YES: Go to STEP 2.
NO: Replace the ABS-ECU and then go to Step 3.








STEP 2. Check the harness wires between ABS-ECU connector A-02 and ABS warning light connector C-102.
Q: Are any harness wires between ABS-ECU connector A02 and ABS warning light connector C-102 damaged?
YES: Repair them and then go to STEP 3.
NO: Go to Step 3.

STEP 3. Check symptoms.
Q: Does the ABS warning light turn off 3 seconds after start-up?
YES: This diagnosis is complete.
NO: Return to STEP 1.