2: ABS Warning Light Does Not Illuminate When Key Is Turned on
INSPECTION PROCEDURE 2: When the Ignition Switch is Turned to the "ON" Position (Engine Stopped or After Start-up), the ABS Warning Light does not Illuminate.
Part 1 of 2
Part 2 of 2
CIRCUIT OPERATION
- The ABS warning light power is supplied from the ignition switch.
- The ABS-ECU controls the continuity to the ABS warning light by fuming the power transistor in the unit "ON" and "OFF" to turn the ABS relay "ON" and "OFF".
TECHNICAL DESCRIPTION (COMMENT)
The cause may be: an open circuit in the light power apply circuit, a blown light bulb, an open circuit in both the circuit between the ABS warning light and the ABS-ECU.
TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Blown fuse
- Damaged wiring harness and connector
- Burnt out ABS warning light bulb
- Malfunction of the ABS relay
DIAGNOSIS
Required Special Tool:
- MB991223: Harness Set
STEP 1. Check the ABS warning light circuit at ABS-ECU connector A-85.
1. Disconnect ABS-ECU connector A-85.
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 16.
NO: Go to Step 2.
STEP 2. Check the circuit at connector C-17.
1. Disconnect connector C-17.
2. Turn the ignition switch to the "ON" position.
Q: Does the ABS warning light illuminate when male pin terminal 5 is grounded?
YES: Go to STEP 4.
NO: Go to Step 3.
STEP 3. 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 16.
NO: Go to Step 10.
STEP 4. Check the ABS relay.
1. Remove the ABS relay.
2. Check the continuity between terminals 3 - 4 when battery voltage is applied between terminals 1 - 2
Q: Is the ABS warning light relay continuity?
YES: Go to Step 7.
NO: Replace the ABS relay. Then go to Step 16.
STEP 5. Check the circuit at ABS relay connector A-35.
1. Disconnect ABS relay connector A-35 and measure at the ABS relay harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 3 and ground. Voltage should be approximately 12 volts (battery positive voltage.)
Q: Is the voltage approximately 12 volts?
YES: Go to Step 8.
NO: Go to Step 6.
STEP 6. Check harness connectors A-35 and C-17 for damage.
Q: Are any connectors damaged?
YES: Repair it and then go to Step 16.
NO: Go to Step 7.
STEP 7. Check the harness wire between ABS relay A-35 and intermediate connector C-17.
Q: Is the harness wire between ABS relay A-35 and intermediate connector C-17 damaged7
YES: Repair it and then go to Step 16.
NO: Go to Step 8.
STEP 8. Check harness connector A-35.
Q: Is connector damage?
YES: Repair or replace it. Then go to Step 16.
NO: Go to Step 9.
STEP 9. Check the harness wire between.
Q: Is the harness wire between ABS relay A-35 and ground damaged?
YES: Repair it and then go to Step 16.
NO: Go to Step 16.
STEP 10. 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-04 terminal 24 and connector C-05 terminal 10. 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 11.
STEP 11. Check the combination meter power supply circuit.
1. Disconnect connector C-04, and check at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 24 and ground. It should be approximately 12 volts (battery positive voltage.)
Q: Is the voltage approximately 12 volts?
YES: Go to Step 12.
NO: Go to Step 14.
STEP 12. Check connectors C-05, C-17, A-35 and A-85.
Check connectors C-05, C-17, A-35 and A-85.
Q: Is any of the connectors damaged?
YES: Repair it and then go to Step 16.
NO: Go to Step 13.
STEP 13. Check the continuity between the combination meter and the ABS-ECU.
Check the continuity between combination meter connector C-05 and ABS-ECU connector A-85.
Q: Is there the continuity between combination meter connector C-05 and ABS-ECU connector A-85?
YES: Go to Step 16.
NO: Repair the harness wire and then go to Step 16.
STEP 14. Check connectors C-04, D-06 and D-08. Check connectors C-04, D-06 and D-08.
Q: Are any of the connectors damaged?
YES: Repair it and then go to Step 16.
NO: Go to Step 15.
STEP 15. 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-04?
YES: Go to Step 16.
NO: Repair the harness wire and then go to Step 16.
STEP 16. Check symptom.
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.