B1437

DTC B1437: Side Impact Sensor (LH) Power Supply Circuit System

Side Impact Sensor (LH) Circuit:

CAUTION: If DTC B1437 is set in the SRS-ECU, always diagnose the CAN main bus line.

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-air-bags should be deployed, it sends a fire signal to the SRS-ECU to deploy the side-airbags. In addition, 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
This DTC is set if the power supply voltage of the side impact sensor (LH) drops below the rated value for a continuous period of 5 seconds or more. However, DTC B1437 will be automatically cleared and the SRS warning light will switch off if the condition returns to normal.

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: V.C.I.
- MB991827: MUT-III USB Cable
- MB991910: MUT-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 the side impact sensor (LH) power supply circuit. Measure the voltage at the side impact sensor (LH) connector D-17.

1. Disconnect the negative battery terminal.

2. Disconnect side impact sensor (LH) connector D-17, and measure at the wiring harness side.
3. Connect the negative battery terminal.
4. Turn the ignition switch to the "ON" position.

CAUTION: Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.

5. Measure the voltage between the D-17 harness side connector terminal 2 and body ground.

6. A wave pattern of oscilloscope iterates an amplitude of 6 - 12 volts.

Q: Is the check result normal?

YES: Replace the side impact sensor (LH). 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-122 (terminal No.19 and 20) and side impact sensor (LH) connector D-17(terminal No.1 and 2).

Q: Are the harness wires between SRS-ECU connector C-122 (terminal No.19 and 20) 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 B1437 sets, replace the SRS-ECU. Then go to Step 5.

NO: Replace the harness wires between SRS-ECU connector C-122 and side impact sensor (LH) connector D-17. Then go to Step 5.

STEP 5. Recheck for diagnostic trouble code.