B1409

DTC B1408: Front Impact Sensor (RH) (Squib) for Power Supply Circuit
DTC B1409: Front Impact Sensor (RH) (Squib) for Communication System

Front Impact Sensor Circuit:

CAUTION: If DTC B1408 or B1409 is set in the SRS-ECU, always diagnose the CAN main bus line.

CIRCUIT OPERATION
The front 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 front air bags should be deployed, it sends a fire signal to the SRS-ECU to deploy the front air bags. In addition, the CPU diagnoses the internal components of the front impact sensor. If a malfunction occurs, it requests the SRS-ECU to set a diagnostic trouble code.

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

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

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

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.

1. Connect scan tool MB991958. Refer to "How to connect the scan tool."
2. Turn the ignition switch to the "ON" position.
3. Diagnose the CAN bus line.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the CAN bus line found to be normal?

YES: Go to Step 2.

NO: Repair the CAN bus line (Refer to Information Bus, Diagnosis).

STEP 2. 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 3.

NO: There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).

STEP 3. Check for any diagnostic trouble code. (Using scan tool MB991958, read the diagnostic trouble code.)

Check the front impact sensor (RH).
1. Disconnect the negative battery terminal.
2. Temporarily replace the front impact sensor (RH) with the front impact sensor (LH).
3. Connect the negative battery terminal.
4. Erase diagnostic trouble code from memory, and check the diagnostic trouble code.

Q: Is DTC B1418 or B1419 set?

YES: Replace the front impact sensor (RH) with a new one. Then go to Step 5.

NO: Go to Step 4.

STEP 4. Check the harness wires for open circuit or short circuit between SRS-ECU connector C-123 (terminal No.47 and 48) and front impact sensor (RH) connector A-30 (terminal No.1 and 2).

NOTE: After inspecting intermediate connector C-10 inspect the wiring harness. If the intermediate connector C-10 is damaged, repair or replace it.

Q: Are the harness wires between SRS-ECU connector C-123 (terminal No.47 and 48) and front impact sensor (RH) connector A-30 (terminal No.1 and 2) in good condition?

YES: Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1408 or B1409 sets, replace the SRS-ECU. Then go to Step 5.

NO: Replace the harness wires between SRS-ECU connector C-123 and front impact sensor (RH) connector A-30. Then go to Step 5.

STEP 5. Recheck for diagnostic trouble code.