SRS Warning Light Drive Circuit System Fault 1 (Light Does Not Switch Off)

DTC 43: SRS Warning Light Drive Circuit System Fault 1 (Light does not Switch Off.)

SRS Warning Light Drive Circuit Part 1:

SRS Warning Light Drive Circuit Part 2:

CIRCUIT OPERATION
- Power for the SRS warning light is supplied from the ignition switch (IG1).
- The SRS warning light illuminates when the ignition switch is turned to the "ON" position and goes out after approximately seven seconds if there is not a malfunction in the SRS system.

DTC SET CONDITIONS
This DTC is set when a short to ground occurs in the harness between the SRS warning light and SRS-ECU while SRS-ECU is monitoring the light and the light is ON. However, if the vehicle condition returns to normal, DTC 43 will be automatically erased, and the SRS warning light will go out.

TROUBLESHOOTING HINTS
- Damaged wiring harnesses or connectors
- Malfunction of the SRS-ECU
- Malfunction of the combination meter

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: MUT-III USB Cable
- MB991911: MUT-III Main Harness B (Vehicles without CAN communication system)

STEP 1. Check SRS-ECU connector C-12 for damage.




1. Disconnect SRS-ECU connector C-12.




2. Check the short spring for warning light inside the harness connector for improper contact or deformation.

Q: Is SRS-ECU connector C-12 in good condition?

YES: Then go to Step 2.

NO: Repair or replace the SRS-ECU connector C-12. Then go to Step 4.

STEP 2. Check the SRS warning light.

1. Disconnect the negative battery cable.




2. Disconnect the combination meter connector C-02.
3. Connect the negative battery cable.
4. Turn the ignition switch to the "ON" position.

Q: Does the SRS warning light go out?

YES: Go to Step 3.

NO: Replace the combination meter. (Refer to Combination Meter Assembly) Then go to Step 4.







STEP 3. Check the harness for short circuit to ground between SRS-ECU connector C-12 (terminal No.8) and combination meter connector C-02 (terminal No.36).

Q: Is the harness wire between the SRS-ECU connector C-12 (terminal No.8) and combination meter connector C-02 (terminal No.36) in good condition?

YES: Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC 43 sets, replace the SRS-ECU. Then go to Step 4.

NO: Repair the harness wire between SRS-ECU connector C-12 and combination meter connector C-02. Then go to Step 4.

STEP 4. Recheck for diagnostic trouble code.

Q: Is DTC 43 set?

YES: Return to Step 1.

NO: The procedure is complete. (If no malfunctions are found in all steps, an intermittent malfunction is suspected. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction)