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DTC B1451: Curtain air bag module (LH) (squib) system (open circuit of squib circuit)
 
 
cautionIf DTC B1451 is stored 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 and/or quarter panel, and the G-sensor in the SRS-ECU. If the impact is over a predetermined level, the SRS-ECU sends an ignition signal. At this time, 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 stored if there is abnormal resistance between the input terminals of the curtain air bag module (LH) (squib).
 
 
TROUBLESHOOTING HITS
  • Open circuit in the curtain air bag module (LH) (squib) circuit
  • Improper connector contact
  • Malfunction of the SRS-ECU
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-III), diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
Connect scan tool (M.U.T.-III). Refer to "How to connect the scan tool ."
(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.
Is the CAN bus line found to be normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C, Diagnosis ).
 
STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is stored.
(1) Erase the DTC.
(2) Turn the ignition switch to the "ON" position.
(3) Check if the DTC is stored.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the DTC stored?
Go to Step 3.
There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
 
STEP 3. Diagnosis check by dummy resistor connection.
(1) Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(2) Use the flat-tipped screwdriver to pull out the locking button of curtain air bag module connector to the direction of the arrow. After releasing the lock, disconnect the connector.
(3) Connect the dummy resistor (Special tool: MB991865) to the resistor harness (Special tool: MB991884).
(4) Connect the resistor harness (special tool) to curtain air bag module (LH) connector.
(5) Connect the negative battery terminal.
(6) After erasing the DTC memory, check the DTC again.
(7) Disconnect the negative battery terminal.
Is the DTC B1451 stored?
Go to Step 4.
Replace the curtain air bag module (LH) (Refer to ).
 
STEP 4. Resistance measurement at the SRS-ECU connector and the curtain air bag module (LH) connector.
(1) Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(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 SRS-ECU connector.
(3)
dangerTo release SRS-ECU wiring harness side connector short spring in the following operations, disconnect curtain air bag module connector in advance, and keep the squib circuit shorted.
Use the flat-tipped screwdriver to pull out the locking button of curtain air bag module (LH) connector to the direction of the arrow. After releasing the lock, disconnect the connector.
(4)
cautionThe short spring may not be released due to the insufficient insertion. Therefore, insert the insulator for 4 mm (0.16 inch) or more.
Insert an insulator [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] such as cable tie between the CLS+, CLS- line and the short spring, and release the short spring.
(5) Connect the resistor harness (Special tool: MB991884) to the removed curtain air bag module (LH) connector.
noteWhen the resistor harness is connected, the terminal No. of connected side and the CLS+, CLS- line of resistor harness connector will become inverted.
(6) Take the following measurements.
  • Continuity CLS+ line between SRS-ECU wiring harness side connector and the resistor harness connector
  • Continuity CLS- line between SRS-ECU wiring harness side connector and the resistor harness connector
OK: Continuity (less than 2 Ω)
Is the check result normal?
Go to Step 5.
Repair the wiring harness.
 
STEP 5. Recheck for diagnostic trouble code.
Check again if the DTC is stored.
(1) Erase the DTC.
(2) Turn the ignition switch to the "ON" position.
(3) Check if the DTC is stored.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is DTC B1451 stored?
Replace SRS-ECU (Refer to ).
Intermittent Malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).