B1B1B

DTC B1B1B: Curtain Air Bag Module (LH) (Squib) System (Short Circuit between Squib Circuit Terminals)

CAUTION:
If DTC B1B1B 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 side impact sensors installed on the lower side of the center pillar. If the impact is over a predetermined level, the SRS-ECU sends an ignition signal. At this time, if the side collision safing G-sensor is on, the SRS air bag will inflate.
- The ignition signal is input to the curtain air bag module (LH) to inflate the curtain air bag.

DTC SET CONDITIONS

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

TROUBLESHOOTING HITS

- Improper engaged connector or defective short spring*
- Short circuit between the curtain air bag module (LH) (squib) circuit terminals
- Damaged connector(s)
- Malfunction of the SRS-ECU

NOTE:
*: The squib circuit connectors integrate a "short" spring (which prevents the air bag from deploying unintentionally due to static electricity by shorting the positive wire to the ground wire in the squib circuit when the connectors are disconnected) (Refer to Description and Operation).
Therefore, if connector C-36, D-15 or F-28 is damaged or improperly engaged, the short spring may not be released when the connector is connected.

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
- MB991866: Resister harness

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.

(1)
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.

Connect scan tool MB991958. Refer to "How to connect the scan tool Reading and Clearing Diagnostic Trouble Codes."
(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 CAN Bus Diagnostics Chart).

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 How to Cope With Intermittent Malfunctions).
STEP 3. Check SRS-ECU connector C-36, curtain air bag module (LH) connector F-28 and intermediate connector D-15.

(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-36 SRS-ECU connector. Then connect the connector.

(3)After disconnecting the F-28 harness side connectors, connect the connectors again. For the F-28 connector disconnection, use a flat-tipped screwdriver to unlock the locking button at the harness side connector by withdrawing it to ward you in two stages, and then disconnect the connector.

(4)Disconnect the D-15 connector's, and then reconnect them. Unlock the connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect the connector.
(5)Connect the negative battery terminal.
(6)After erasing the diagnostic trouble code memory, check the diagnostic trouble code again.
(7)Disconnect the negative battery terminal.

Q. Is DTC B1B1B set?

YES Go to Step 4.

NO Intermittent Malfunction How to Cope With Intermittent Malfunctions).

STEP 4. Check by dummy resistor connection.

(1)Disconnect the negative battery terminal.

(2)Unlock D-15 intermediate connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect the connector.

(3)Connect special tool MB991865 to special tool MB991866.
(4)
CAUTION:
Do not insert a probe into the terminal from its front side directly, as the connector contact pressure may be weakened.

Insert the probe of resistor harness, to which the dummy resistor is installed, from the back of D-15 intermediate connector (floor harness side).
(5)Connect the negative battery terminal.
(6)After erasing the diagnostic trouble code memory, check the diagnostic trouble code again.

Q. Is DTC B1B1B set?

YES Go to Step 5.

NO Go to Step 6.

STEP 5. Resistance measurement at the C-36 SRS-ECU connector.

(1)Disconnect the negative battery terminal.

(3)DANGER:
To prevent the air bag from deploying unintentionally, disconnect the intermediate connector D-15 to short the squib circuit.

Unlock D-15 intermediate connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect the connector.

(4)
CAUTION:
The short spring may not be released due to the insufficient insertion. Therefore, insert the insulator for 4 mm (0.16 inch) or more.

Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminal 41, 42 and the short spring to release the short spring.

(5)Check for continuity between the C-36 wiring harness side connector terminal No. 41 and No. 42.
It should be open circuit.

Q. Is it open circuit?

YES Go to Step 7.

NO Repair the wiring harness.

STEP 6. Short circuit check between the F-28 curtain air bag module harness side connector and the D-15 intermediate harness.

(1)Disconnect the negative battery terminal.

(2)DANGER:
To prevent the air bag from deploying unintentionally, disconnect the curtain air bag module connector F-28 to short the squib circuit.

Disconnect curtain air bag module (LH) F-28. 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)Unlock D-15 intermediate connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect the connector.

(4)Because the short spring is installed to the D-15 intermediate connector (curtain air bag harness side), 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)
CAUTION:
Do not insert a probe into the terminal from its front side directly, as the connector contact pressure may be weakened.

Check for continuity between the D-15 intermediate connector (curtain air bag harness side) terminal No.1 and 2.
It should be open circuit.

Q. Is it open circuit?

YES Replace the curtain air bag module (LH) (Refer to Removal and Installation).
Then go to Step 7.

NO Repair the wiring harness.

STEP 7. 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 B1B1B set?

YES Replace SRS-ECU (Refer to Service and Repair).
NO Intermittent Malfunction How to Cope With Intermittent Malfunctions).