2: ABS Warning Light Does Not Illuminate When Key Is Turned On
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 power supply circuit at ABS-ECU connector A-02.
1. Disconnect connector A-02 and measure at the harness side
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 21 and ground.
The ABS warning lamp should illuminate
If it does not illuminate, go to Step 2.
If it illuminates, replace the hydraulic unit (integrated with ABS-ECU). Then go to Step 9.
STEP 2 Check the ABS warning light bulb.
1. Remove the combination meter.
2. Check the ABS warning light bulb.
If the bulb is burned out, replace the bulb. Then go to Step 9.
If the bulb is not burned out, 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-41 terminal 52 and connector C-42 terminal 24. The resistance reading at this time should be much the same as the resistance measured at step (2).
If the two resistance values are extremely different each other, replace the combination meter (printed circuit board).
If the two resistance values are much the same, go to Step 4.
STEP 4 Check the combination meter power supply circuit.
1. Disconnect connector C-41, 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.)
If not approximately 12 V, go to Step 7.
If approximately 12 V, go to Step 5.
STEP 5 Check connectors C-42, C-94, and A-02.
Check connectors C-42, C-94, and A-02. (Refer to Harness Connector Inspection). Initial Inspection and Diagnostic Overview
If any of the connectors is damaged, repair it. Then go to Step 9.
If all of the connectors are not damaged, go to Step 6.
STEP 6 Check the continuity between the combination meter and the ABS-ECU.
Check the continuity between combination meter connector C-42 and ABS-ECU connector A-02.
If open circuit, repair the wire. Then go to Step 9.
STEP 7 Check connectors C 41, C-104, and C-101.
Check connectors C-41, C-104, and C-101 . (Refer to Harness Connector Inspection.) Initial Inspection and Diagnostic Overview
If any of the connectors are damaged, repair it. Then go to Step 9.
If all of the connectors are not damaged, go to Step 8.
STEP 8 Check the continuity between the ignition switch (IG1) and the combination meter.
Check the continuity between the ignition switch (IG1) and combination meter connector C-41.
If open circuit, repair the wire. Then go to Step 9.
If less than 2 ohm, go to Step 9.
STEP 9. Check symptoms
Confirm the ABS warning light illuminates for 3 seconds when the ignition switch is turned to the "ON" position with engine stopped or upon start-up.