B1C3A

DTC B1C3A: Driver's Pre-tensioner (Squib) System (Squib Circuit Open)

Seat Belt Pre-Tensioner (LH)(Squib) Circuit:

CAUTION: If DTC B1C3A is set in the SRS-ECU, always diagnose the CAN main bus line.

SRS AIR B CIRCUIT OPERATION
The SRS-ECU judges how severe a collision is by detecting signals from the front impact sensors and the front air bag analog G-sensor. If the impact is over a predetermined level, the SRS-ECU sends an ignition signal. At this time, if the front air bag safing G-sensor is on, the pre-tensioner will deploy.

DTC SET CONDITIONS
This DTC is set if there is abnormal resistance between the input terminals of the driver's seat belt pre-tensioner (squib).

TROUBLESHOOTING HITS
- Improper connector contact
- Open circuit in the driver's seat belt pre-tensioner (squib) circuit
- 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)
- MB991865: Dummy resistor
- MB991884: Resister harness

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". Scan Tool Connecting
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 Controller area network 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 general (body and chassis)-How to Cope with Intermittent Malfunction).

STEP 3. Check the driver's seat belt pre-tensioner.

1. Disconnect the negative battery terminal.




2. Disconnect driver's seat belt pre-tensioner connector D-21. Use a flat-tipped screwdriver to unlock the locking button at the harness side connector by withdrawing it toward you in two stages, and then disconnect the connector.




3. Connect special tool MB991865 to special tool MB991884.
4. Connect special tool MB991884 to the D-21 harness side connector.
5. Connect the negative battery terminal.
6. Erase diagnostic trouble code memory, and then check the diagnostic trouble code.

Q: Is DTC B1C3A set?

YES : Go to Step 4.

NO : Replace the driver's seat belt with pre-tensioner. Then go to Step 5.

STEP 4. Check the harness for open circuit between SRS-ECU connector C-30 (terminal No.45 and 46) and the driver's seat belt
pre-tensioner D-21 (terminal No.1 and 2).




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-30 SRS-ECU connector.




2. Disconnect SRS-ECU connector C-30 and driver's seat belt pretensioner connector D-21, and measure at the wiring harness side. For connector D-21, use a flat-tipped screwdriver to unlock the locking button at the harness side connector by withdrawing it toward you in two stages, and then disconnect the connector.




3. Connect D-21 harness side connector to special tool MB991884.






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

4. Check for continuity between the following terminals. It should be less than 2 ohms.
- SRS-ECU connector C-30 (terminal No.45) and the special tool (terminal No.2)
- SRS-ECU connector C-30 (terminal No.46) and the special tool (terminal No.1)

Q: Does continuity exist?

YES : Erase the diagnostic trouble code memory, and recheck if any DTC set. If DTC B1C3A set, replace the SRS-ECU. Then go to Step 5.

NO : Replace harness wires between SRS-ECU connector C-30 and driver's seat belt pretensioner connector D-21. Then go to Step 5.

STEP 5. 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 DTC B1C3A set?

YES : Return to Step 1

NO : The procedure is complete.