B1C2A
DTC B1C2A: Side-air bag Module (LH) (Squib) System (Short Circuit between Squib Circuit Terminals)
CAUTION:
If DTC B1C2A is set in the SRS-ECU, always diagnose the CAN bus lines.
CIRCUIT OPERATION
- The SRS-ECU judges how severe a collision is by detecting signals from the side impact sensor 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 side-air bag module to inflate the side-air bag.
DTC SET CONDITIONS
This DTC is set if there is abnormal resistance between the input terminals of the side-air bag module (LH) (squib).
TROUBLESHOOTING HINTS
- Improper engaged connector or defective short spring*
- Short circuit between the side-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 or D-34 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.
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 Reading and Clearing Diagnostic Trouble Codes."
(2)Connect scan tool MB991958 to the data link connector.
(3)Turn the ignition switch to "ON" position.
(4)Diagnose the CAN bus line.
Q. Is the check result satisfactory?
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 and side-air bag module (LH) connector D-34.
(1)Disconnect the negative battery terminal.
(2)Disconnect the D-34 side-airbag module connector, 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.
(3)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.
(4)Connect the negative battery terminal.
(5)Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
Q. Is DTC B1C2A out put?
YES Go to Step 4.
NO The procedure is complete. It is assumed that DTC B1C2A set because connector C-36 or D-34 was engaged improperly.
STEP 4. Check the side-air bag module (LH).
(1)Disconnect the negative battery terminal.
(2)Unlock D-34 side-airbag module 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 test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
Insert special tool MB991866 into the D-34 harness side connector by backprobing.
(5)Connect the negative battery terminal.
(6)Erase diagnostic trouble code memory, and check the diagnostic trouble code.
Q. Is DTC B1C2A set?
YES Go to Step 5.
NO Replace the front seatback Front Seat Assembly Disassembly and Assembly).
Then go to Step 7.
STEP 5. Check the side-air bag module (LH) circuit. Measure the resistance at the SRS-ECU connector C-36.
(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.
(3)DANGER:
To prevent the air bag from deploying unintentionally, disconnect the side-air bag module (LH) connector D-34 to short the squib circuit.
Unlock D-34 side-airbag module connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect the connector.
(4)
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.
Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminals 31, 32 and the short spring to release the short spring.
(5)Check for continuity between C-36 harness side connector terminals 31 and 32.
It should be an open circuit.
Q. Is it open circuit?
YES Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
If DTC B1C2A sets, replace the SRS-ECU (Refer to Service and Repair). Then go to Step 7.
NO Go to Step 6.
STEP 6. Check the harness wires for short circuit between SRS-ECU connector C-36 (terminal No.31 and 32) and side-air bag module (LH) connector D-34 (terminal No.2 and 1).
Q. Is the check result normal?
YES Go to Step 7.
NO Repair the harness wires between SRS-ECU connector C-36 and side-air bag module
(LH) connector D-34. Then go to Step 7.
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 B1C2A set?
YES Return to Step 1.
NO The procedure is complete.