B1B56

DTC B1B54: Seat Belt Switch (RH) Circuit (Ground Side) Shorted
DTC B1B55: Seat Belt Switch (RH) Circuit (Power Supply Side) Shorted
DTC B1B56: Seat Belt Switch (RH) Circuit Open

Seat Belt Switch Circuit:

CAUTION: If DTC B1B54, B1B55 or B1B56 are set in the SRS-ECU, always diagnose the CAN main bus lines.

CIRCUIT OPERATION
The SRS-ECU determines whether the seat belt is fastened or not according to the connection location of the seat belt switch in the seat buckle.

DTC SET CONDITIONS
DTC is set when the resistance between input terminals of the seat belt switch in the SRS-ECU is without the standard value.

TROUBLESHOOTING HINTS
- Malfunction of the seat belt switch
- Damaged wiring harnesses or connectors
- Malfunction of the SRS-ECU

DIAGNOSIS

Required Special Tools:
- MB991222: Probe
- 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. 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. Connect scan tool MB991958 to the data link connector.
3. Turn the ignition switch to the "ON" position.
4. Diagnose the CAN bus line.
5. Turn the ignition switch to the "LOCK" (OFF) position.

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

YES : Go to Step 3.

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 "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 passenger's seat belt switch.




Disconnect passenger's seat belt switch connector D-33. Then check continuity between the switch terminals.






Q: Is Passenger's seat belt switch in good condition?

YES : Go to Step 4.

NO : Replace inner seat belt (Refer to Interior Front Seat Belt).

STEP 4. Check the Passenger's seat belt switch circuit D-33. Measure the resistance at SRS-ECU connector C-30

1. Disconnect passenger's seat belt switch connector D-33.




2. Install the passenger's seat belt to the Passenger's seat be switch.
3. Disconnect SRS-ECU connector C-30 and measure at the harness side.




4. 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.




5. Measure the resistance between terminal 55, 58 and body ground.
It should be an open circuit.




6. Measure the resistance between terminal 55 and terminal 58.
Resistance should be less than 2 ohms.




7. Remove the passenger's seat belt from the passenger's seat belt switch.
8. Disconnect SRS-ECU connector C-30 and measure at the harness side.




9. 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.




10. Measure the resistance between terminal 55, 58 and body ground.
It should be an open circuit.




11. Measure the resistance between terminal 55 and terminal 58.
It should be an open circuit.

Q: Does the resistance meet the value above?

YES : Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1B50, B1B51or B1B52 are set, replace the SRS-ECU. Then go to Step 6.

NO : Go to Step 5.

STEP 5. Check the harness wires between SRS-ECU connector C-30 (terminal No.55 and 58) and Passenger's seat belt switch connector D-33
(terminal No.1 and 2).

Q: Are harness wires between SRS-ECU connector C-30 (terminal No.55 and 58) and passenger's seat belt switch connector D-33 (terminal No.1 and 2) in good condition?

YES : Go to Step 6.

NO : Replace the harness wires between SRS-ECU connector C-30 and passenger's seat belt switch connector D-33. Then go to Step 6.

STEP 6. 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 B1B54, B1B55 or B1B56 set?

YES : Return to Step 1.

NO : The procedure is complete.