3: ABS Warning Light Remains Illuminated After Starting Engine

ABS WARNING LIGHT POWER SUPPLY CIRCUIT

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




















CIRCUIT OPERATION
- The ABS-ECU controls the continuity to the ABS warning light by turning the power transistor in the unit "ON" and "OFF" to turn the ABS warning relay "ON" and "OFF."

TECHNICAL DESCRIPTION (COMMENT)
The cause is probably an ABS warning light relay hydraulic unit (integrated with ABS-ECU) malfunction.

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

DIAGNOSIS
Required Special Tool MB991223: Harness Set





STEP 1. Check the ABS warning light relay continuity.
1. Remove the ABS warning light relay.
2. Check the continuity between terminal number 1 and number 3 and between terminal number 5 and number 2 at the ABS warning light relay.
If there is no continuity, replace the ABS warning light. Then go to Step 7.
If there is continuity, go to Step 2.
STEP 2. Check the ABS warning light relay continuity.
1. Remove the ABS warning light relay.
2. Apply the positive terminal of the battery to the No. 1 terminal and the negative terminal to the No. 3 terminal, and then check the continuity between the No. 5 terminal and the No. 2 terminal.
If there is continuity, replace the ABS warning light. Then go to Step 7.
If there is no continuity, go to Step 3.





STEP 3. Check the power supply circuit at the ABS warning light relay connector A-10X.
1. Start the engine.
2. Measure at the relay box in engine compartment side the voltage between the terminal 1 and ground. Voltage should be approximately 12 volts (battery positive voltage).
If not approximately 12 volts, go to Step 4.
If approximately 12 volts, go to Step 5.





STEP 4. Check the harness wire between ignition switch (IG2) and ABS warning light relay connector A-10X
Continuity should exist between the ignition switch (IG2) and terminal 3 of connector A-10X If there is no continuity, repair the harness wire.
Then go to Step 7.
If there is continuity, go to Step 5.








NOTE: After inspecting intermediate connector C-66, C-73 or C-77 inspect the wire. If intermediate connector C-66, C-73 or C-77 is damaged, repair or replace it. If the connector has been repaired or replaced, go to Step 7.








STEP 5. Check the harness wire between ABS-ECU connector A-03 and ABS warning light relay connector A-10X
Continuity should exist between terminal 16 of connector A-03 and terminal 3 of connector A-10X. If there is no continuity, repair the harness wire. Then go to Step 7.
If the harness wire is not damaged, go to Step 6.





NOTE: After inspecting intermediate connector C-05, inspect the wire. If intermediate connector C-05, is damaged, repair or replace it. If the connector has been repaired or replaced, go to Step 7.





STEP 6. Check the harness wire between combination meter connector C-30 and ABS warning light relay connector A-10X.
1. Remove the combination meter.
2. Check the harness wire between combination meter of connector C-30 terminal 8 and ABS warning light relay connector A-10X terminal 5.





Continuity should exist between terminal 8 of connector C-30 and terminal 5 of connector A-10X. If there is no continuity, repair the harness wire. Then go to Step 7.
If there is continuity, replace the ABS-ECU. Then go to Step 7.
STEP 7. Check symptoms
Confirm that the intermediate connectors, the harness wires, the ABS warning light relay and the hydraulic unit (integrated with ABS-ECU) are normal.