Inspection Procedure 2

INSPECTION PROCEDURE 2: When the ignition switch is turned "ON" (engine stopped or after start-up), the ABS warning light does not illuminate.








CIRCUIT OPERATION
- The ABS warning light power is supplied from the ignition switch. The ABS-ECU grounds the circuit to illuminate the light.
- The ABS-ECU illuminates the ABS warning light for 3 seconds while running self-check. This light can be illuminated for 3 seconds upon start-up or ignition switch to the "ON" position, engine stopped.

TECHNICAL DESCRIPTION (COMMENT)
The cause may be: an open circuit in the ABS warning light power supply circuit, a blown ABS warning light bulb, or malfunction of the ABS-ECU.

TROUBLESHOOTING HINTS
The most likely causes for this case:
- Blown fuse
- Damaged wiring harness or connector
- Burnt out ABS warning light bulb
- Malfunction of the 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: Does the ABS warning light illuminate?
YES: Replace the hydraulic unit (integrated with ABS-ECU) and then go to STEP 9.
NO: Go to Step 2.

STEP 2. Check the ABS warning light bulb.
1. Remove the combination meter
2. Check the ABS warning light bulb.
Q: Is the bulb burned out?
YES: Replace the bulb and then go to STEP 9.
NO: Go to Step 3.





STEP 3. Check the combination meter for continuity.
1. Remove the combination meter.
2. Remove the ABS warning light bulb. Then measure the resistance between the bulb terminals.
3. Install the ABS warning light bulb to the combination meter, and then measure the resistance between connector C-101 terminal 52 and connector C-102 terminal 24. The resistance reading at this time should be much the same as the resistance measured at step (2).
Q: Are the two resistance values extremely different each other?
YES: Replace the combination meter (printed circuit board).
NO: Go to Step 4.





STEP 4. Check the combination meter power supply circuit.
1. Disconnect connector C-101, and check at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 52 and ground. It should be approximately 12 V (battery positive voltage.)
Q: Is the voltage approximately 12 V?
YES: Go to STEP 5.
NO: Go to Step 7.











STEP 5. Check connectors C-102, C-212, and A-02. Check connectors C-102, C-212, and A-02.
Q: Is any of the connectors damaged?
YES: Repair it and then go to STEP 9.
NO: Go to Step 6.








STEP 6. Check the continuity between the combination meter and the ABS-ECU. Check the continuity between combination meter connector C102 and ABS-ECU connector A-02.
Q: Is there the continuity between combination meter connector C-102 and ABS-ECU connector A-02?
YES: Go to STEP 9.
NO: Repair the harness wire and then go to Step 9.








STEP 7. Check connectors C-101, C-308, and C-301. Check connectors C-101, C-308, and C-301.
Q: Are any of the connectors damaged?
YES: Repair it and then go to STEP 9.
NO: Go to Step 8.





STEP 8. Check the continuity between the ignition switch (IG1) and the combination meter.
Q: Is there any continuity (less than 2 ohm) between the ignition switch (IG1) and combination meter connector C-101 ?
YES: Go to STEP 9.
NO: Repair the harness wire and then go to Step 9.
STEP 9. Check symptoms
Q: Does the ABS warning light illuminate for 3 seconds when the ignition switch is turned to the "ON" position with engine stopped or upon start-up?
YES: This diagnosis is complete.
NO: Return to STEP 1.