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DTC B1440: Curtain air bag module (RH) (squib) system (short circuit between squib circuit terminals)
 
 
cautionIf DTC B1440 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 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 (RH) 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 (RH) (squib).
 
 
TROUBLESHOOTING HITS
  • Improper engaged connector or defective short spring*
  • Short circuit between the curtain air bag module (RH) (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 ). Therefore, if connector is damaged or improperly engaged, the short spring may not be released when the connector is connected.
 
 
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 electric motor 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 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.
Is the DTC set?
Go to Step 3.
There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
 
STEP 3. Connector check: SRS-ECU, curtain air bag module (RH).
(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. After disconnecting the SRS-ECU connector, connect it again.
(3) After disconnecting the curtain air bag module (RH) harness side connector, connect the connector again. For the curtain air bag module (RH) connector disconnection, use the flat-tipped screwdriver to pull out the harness side connector locking button. After releasing the lock, disconnect the connector.
(4) Connect the negative battery terminal.
(5) After erasing the DTC memory, check the DTC again.
(6) Disconnect the negative battery terminal.
Is DTC B1440 set?
Go to Step 4.
Replace the connector concerned.
 
STEP 4. 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 harness side connector. After releasing the lock, disconnect the curtain air bag module (RH) harness side 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 (RH) connector.
(5) Connect the negative battery terminal.
(6) After erasing the DTC memory, check the DTC again.
Is DTC B1440 set?
Go to Step 5.
Replace the curtain air bag module (RH) (Refer to .)
 
STEP 5. Resistance measurement at the SRS-ECU 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 harness side connector. After releasing the lock, disconnect the curtain air bag module (RH) harness side 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 CRS-, CRS+ line and the short spring, and release the short spring.
(5) Check the continuity between the SRS-ECU wiring harness side connector CRS-, CRS+ line.
OK: No continuity
Is the check result normal?
Go to Step 6.
Repair the wiring harness.
 
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.
Is DTC B1440 set?
Replace SRS-ECU (Refer to ).
Intermittent Malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).