DTC 79

DTC 79: Side-Airbag Module (LH) (Squib) System Fault 5 for Power Supply Circuit

Side Impact Sensor (LH) Power Supply Circuit Part 1:

Side Impact Sensor (LH) Power Supply Circuit Part 2:

CIRCUIT OPERATION
The side impact sensor includes an analog G sensor and CPU, etc. The CPU monitors the analog G sensor output signal. If the CPU judges that the side-airbags should be deployed, it sends a fire signal to the SRS-ECU to deploy the side-airbags. Besides that, the CPU diagnoses the internal components of the side impact sensor. If a malfunction occurs, it requests the SRS-ECU to set a diagnostic trouble code.

DTC SET CONDITIONS
These DTC are set if communication between the side impact sensor (LH) and the SRS-ECU is not possible or communication is faulty.

TROUBLESHOOTING HINTS
- Damaged wiring harnesses or connectors
- Malfunction of the side impact sensor (LH)
- Malfunction of the SRS-ECU

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: MUT-III USB Cable
- MB991911: MUT-III Main Harness B (Vehicles without CAN communication system)

STEP 1. Check the side impact sensor (LH). (Using scan tool MB991958, read the diagnostic trouble code.)

1. Disconnect the negative battery terminal.
2. Replace the side impact sensor (LH) with the side impact sensor (RH).
3. Connect the negative battery terminal.
4. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

Q: Is DTC 89 or 96 set?

YES: Replace the side impact sensor (LH) with a new one. Then go to Step 3.

NO: Go to Step 2.










STEP 2. Check the harness wires for open circuit or short circuit between SRS-ECU connector C-13 (terminal No.34 and 36) and side impact sensor (LH) connector D-17 (terminal No.1 and 2).

NOTE: After inspecting intermediate connector C-128 inspect the wiring harness. If the intermediate connector C-128 is damaged, repair or replace it. Refer to Harness Connector Inspection. Then go to Step 3. If harness wires are in good condition, go to Step 3. If any harness wires between SRS-ECU connector C-13 and side impact sensor (LH) connector D-17 are damaged, repair them or install the sensor cable. Then go to Step 3.

Q: Are the harness wires between SRS-ECU connector C-13 (terminal No.34 and 36) and side impact sensor (LH) connector D-17 (terminal No.1 and 2) in good condition?

YES: Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC 79 or 93 sets, replace the SRS-ECU. Then go to Step 3.

NO: Repair the harness wires between SRS-ECU connector C-13 and side impact sensor (LH) connector D-17. Then go to Step 3.

STEP 3. Recheck for diagnostic trouble code.

Q: Is DTC 79 or 93 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)