Inspection Procedure 3

Inspection procedure 3:The SRS Warning Light does not Illuminate.

SRS Warning Light Circuit (part 1):

SRS Warning Light Circuit (part 2):

CIRCUIT OPERATION
- 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.
- SRS-ECU sends the SRS warning light signal to the combination meter via the CAN communication.
- As a cause, the failure of CAN bus line, combination meter, or SRS-ECU is suspected.

TROUBLESHOOTING HINTS
- Damaged wiring harness and connectors
- Combination meter malfunction
- Malfunction of SRS-ECU

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.






CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

Use scan tool MB991958 to diagnose the CAN bus lines.

1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Diagnose the CAN bus line.

Q: Is the check result satisfactory?

YES: Go to Step 2.

NO: Repair the CAN bus line (Refer to Controller Area Network (CAN), Diagnosis).

STEP 2. SRS warning light check

1. Disconnect the negative battery terminal.




2. While pushing the part "A" indicated in the figure of the harness side connector, turn the lock lever to the direction of the arrow to release the lock lever, and disconnect the C-37 SRS-ECU connector.
3. Connect the negative battery terminal.
4. Ignition switch: ON

Q: Does the lamp illuminate?

YES: Replace SRS-ECU.

NO: Go to Step 3.

STEP 3. Wiring harness inspection between fusible link (34) and C-04 combination meter connector terminal No. 2

NOTE: Prior to the wiring harness inspection, check the ETACS-ECU connectors C-309 and C-317, and repair if necessary.

- The SRS warning light inspection for open and short circuit

Q: Is the check result normal?

YES: Replace the combination meter. (Refer to Chassis Electrical, Combination Meter.)

NO: Repair the wiring harness.