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

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

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 an open circuit is detected for a continuous period of five seconds while the SRS-ECU is monitoring the SRS warning light and the light is OFF. (transistor OFF.) If the vehicle condition returns to normal, DTC 43 will be automatically erased, and the SRS warning light will switch off.

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

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991911: M.U.T.-III Main Harness B

STEP 1. Check the SRS warning light.




1. Connect the negative battery terminal.
2. Disconnect SRS-ECU connector C-12.
3. Turn the ignition switch to the "ON" position.

Q: Does the warning light illuminate?

YES: Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC 43 set, replace the SRS-ECU. Then go to Step 6.

NO: Go to Step 2.

STEP 2. Check the ground line at the SRS-ECU connector C-12.




1. Disconnect the negative battery terminal.
2. Disconnect SRS-ECU connector C-12.

CAUTION: Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.




3. Check for continuity between C-12 harness connector terminal 7 and ground. It should be less than 2 ohms.

Q: Does continuity exist?

YES: Go to Step 3.

NO: Go to Step 5.




STEP 3. Check the SRS warning light bulb.

Q: Has the SRS warning light bulb blown?

YES: Replace the SRS warning light bulb. Then go to Step 6.

NO: Go to Step 4.
















STEP 4. Check the harness for open circuit between ignition switch connector C-208 (terminal No.2) and combination meter connector C-01 (terminal No.9), and between combination meter connector C-02 (terminal No.36) and SRS-ECU connector C-12 (terminal No.8).

NOTE: After inspecting intermediate connectors C-01, C-02, C-23, C-211, C-214 inspect the wiring harness. If intermediate connectors C-01, C-02, C-23, C-211, C-214 are damaged, repair or replace them. Refer to Harness Connector Inspection.

Q: Are the harness wires between SRS-ECU connector C-12 and the ignition switch connector C-208 in good condition?

YES: Replace the combination meter (Refer to Combination Meters Assembly). Then go to Step 6.

NO: Repair the harness wires between SRS-ECU connector C-12 and the ignition switch connector C-208. Then go to Step 6.







STEP 5. Check the harness for open circuit between SRS-ECU connector C-12 (terminal No.7) and ground.

Q: Is the harness wire between SRS-ECU connector C-12 (terminal No.7) and ground in good condition?

YES: Go to Step 6.

NO: Repair the harness wires between SRS-ECU connector C-12 and ground. Then go to Step 6.

STEP 6. Recheck for diagnostic trouble code.
Check again if the DTC is set.




1. Erase the DTC.
2. Turn the ignition switch to the "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.

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).