Inspection Procedure 2
Inspection procedure 2: Power supply circuit systemIG1 Power Supply Circuit:
CIRCUIT OPERATION
- The SRS-ECU is energized by the ignition switch (IG1) through multi-purpose fuse 18 and the SRS-ECU terminal 61 and multi-purpose fuse 12 and the SRS-ECU terminal 62.
- If the power supply to the SRS-ECU has failed, scan tool (M.U.T.-III Sub Assembly) will not be able to communicate with it.
TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CASE:)
- Damaged wiring harness or connector
- Defective battery
- Charging system failed
- Malfunction of the 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. Resistance measurement at the C-37 SRS-ECU connectors
1. 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 connectors.
2. Take the measurements below at the C-37 wiring harness side connectors.
- Continuity between C-37 wiring harness side connector terminal No. 17 and body ground
OK: Continuity (Less than 2 ohms)
Q: Is the check result normal?
YES: Go to Step 2.
NO: Repair the wiring harness between the C-37 SRS-ECU connector terminal No. 17 and body ground.
STEP 2. Wiring harness check between the C-36 SRS-ECU connector terminal Nos. 61 and 62 and the ignition switch IG1
NOTE: Prior to the wiring harness inspection, check the ETACS-ECU connectors C-309, C-313 and C-317, and repair if necessary.
- Check the power supply line for open and short circuit.
Q: Is the check result normal?
YES: Go to Step 3.
NO: Repair the wiring harness.
STEP 3. Retest the system
Q: Is the communication between scan tool and SRS-ECU possible?
YES: Intermittent malfunction (Refer to general (Body and Chassis), How to Use Troubleshooting/Inspection Service Points -How to Cope with Intermittent Malfunction.)
NO: Replace SRS-ECU.