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

DTC B1551: 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). 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. Connect the negative battery terminal.
3. Disconnected the SRS-ECU connector C-115.
4. 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 B1551 sets, replace the SRS-ECU. Then go to Step 4.

NO: Go to Step 3.










STEP 3. Check the harness for open circuit between ignition switch connector C-303 (terminal No.2) and combination meter C-04 (terminal 4.2), and between combination meter C-05 (terminal No.11) and SRS-ECU connector C-115 (terminal No.26).






NOTE: After inspecting combination meter and connectors C-05, C-04 junction block connectors C-205, C-203, inspect the wiring harness. If intermediate connectors C-05, C-04, C-205, C-203 are damaged, repair or replace them. Refer to Harness Connector Inspection. Then go to Step 4.

Q: Are the harness wires between SRS-ECU connector C-115 (terminal No.26) and the ignition switch connector C-303 (terminal No.2) in good condition?

YES: Replace the combination meter (Refer to Combination Meters Assembly and Vehicle Speed Sensor). Then go to Step 4.

NO: Repair the harness wires between SRS-ECU connector C-115 and the ignition switch connector C-303. Then go to Step 4.

STEP 4. 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.