B1B11

DTC B1B11: Driver's Knee Air Bag (Squib) System (Shorted To Squib Circuit Power Supply)

Knee Air Bag Module (Squib) Circuit:

CAUTION: If DTC B1B11 is set in the SRS-ECU, always diagnose the CAN main bus line.

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 knee air bag module will deploy.

DTC SET CONDITIONS
This DTC is set if there is abnormal resistance between the input terminals of the knee air bag module (squib).

TROUBLESHOOTING HITS
- Damaged wiring harnesses or connectors
- Short to power supply in the knee air bag module (squib) harness
- 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." How To Connect The Scan Tool (M.U.T.-III)
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.

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.

STEP 3. Check the knee air bag module.

1. Disconnect the negative battery terminal.







2. Disconnect knee air bag module connector C-39. 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 C-39 harness side connector.
5. Connect the negative battery terminal.
6. Erase diagnostic trouble code memory, and check the diagnostic trouble code.

Q: Is DTC B1B11 set?

YES : Go to Step 4.

NO : Replace the driver's knee air bag module. Then go to Step 6.

STEP 4. Check the knee air bag module circuit. Measure the voltage at the SRS-ECU connector C-37.

1. Disconnect the negative battery terminal.







2. 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-37 SRS-ECU connector.

DANGER: To prevent the knee air bag module from deploying unintentionally, disconnect the knee air bag module connector C-39 to short the squib circuit.







3. Disconnect knee air bag module connector C-39. 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.

CAUTION: Insert an insulator such as a cable tie to a depth of 4mm (0.16 inch) or more, otherwise the short spring will not be released.







4. Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminals 1, 2 and the short spring to release the short spring.
5. Connect the negative battery terminal.
6. Ignition switch: ON.







7. Measure the voltage between C-37 harness side connector terminals 1, 2 and body ground. Voltage should measure 1 volt or less.

Q: Is the measured voltage within the specified range?

YES : Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1B11 sets, replace the SRS-ECU. Then go to Step 6.

NO : Go to Step 5.

STEP 5. Check the harness wires for short circuit to power supply between SRS-ECU connector C-37 (terminal No.1 and 2) and knee air bag module connector C-39 (terminal No.2 and 1).

Q: Is the check result normal?

YES : Go to Step 6.

NO : Repair the harness wires between SRS-ECU connector C-37 and knee air bag module connector C-39. 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 B1B11 set?

YES : Return to Step 1.

NO : The procedure is complete.