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

DTC B1551: 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 B1551 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
- MB991910: MUT-III Main Harness A (Vehicles with CAN communication)

STEP 1. 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 the DTC set?

YES: Go to Step 2.

NO: There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to How to Cope with Intermittent Malfunction).

STEP 2. Check the SRS warning light




1. Disconnect the negative battery terminal.
2. Disconnect the combination meter connector C-04.
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 Meters Assembly). Then go to Step 7.







STEP 3. Check the harness for short circuit between ignition switch connector C-303 (terminal No.2) and combination meter connector C-04 (terminal no.42).






NOTE: After inspecting junction block connectors C-205 and C-203, inspect the wiring harness. If intermediate connectors C-205, C-203 are damaged, repair or replace them. Refer to Harness Connector Inspection. Then go to Step 7.

Q: Is the harness wire between the ignition switch connector C-303 (terminal No.2) and combination meter connector C-04 (terminal no.42) in good condition?

YES: Go to Step 4.

NO: Repair the harness wire between ignition switch connector C-303 and combination meter connector C-04. Then go to Step 7.




STEP 4. Check combination meter connector C-05.

Q: Is the connector correctly engaged?

YES: Go to Step 5.

NO: Engage the connector correctly. Then go to Step 7.




STEP 5. Check SRS-ECU connector C-115.

Q: Is the connector correctly engaged?

YES: Go to Step 6.

NO: Engage the connector correctly. Then go to Step 7.







STEP 6. Check the harness for short circuit between SRS-ECU connector C-115 (terminal No.26) and combination meter connector C-05 (terminal no.11).

Q: Is the harness wire between the SRS-ECU connector C-115 (terminal No26.) and combination meter connector C-05 (terminal no.11) in good condition?

YES: Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1551 sets, replace the SRS-ECU. Then go to Step 7.

NO: Repair the harness wire between SRS-ECU connector C-115 and combination meter connector C-05. Then go to Step 7.

STEP 7. 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 B1551 set?

YES: Return to Step 1.

NO: The procedure is complete.