DTC B1631: Driver's knee air bag module (squib) system (short circuit between squib circuit terminals): Diagnosis

WARNING: This page is about a different car, the 2014 Mitsubishi Outlander. However, it is still accessible from the selected car via links, so may be relevant.

STEP 1. Using scan tool (M.U.T.-III), diagnose the CAN bus line.
CAUTION: To 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).
1. 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.
Q: Is the CAN bus line found to be normal?
1. YES: Go to Step 2.
2. NO: Repair the CAN bus line (Refer to 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 "ON" position.
3. Check if the DTC is stored.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC stored?
1. YES: Go to Step 3.
2. NO: There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
STEP 3. Connector check: SRS-ECU, knee air bag module.
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.
  
  Fig 1: Disconnecting SRS-ECU Connector
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
3. After disconnecting the knee air bag module harness side connector, connect the connector again. For the knee air bag module harness side connector disconnection, use the flat-tipped screwdriver to pull out the harness side connector locking button. After releasing the lock, disconnect the harness side connector.
4. Connect the negative battery terminal.
5. After erasing the DTC memory, check the DTC again.
6. Disconnect the negative battery terminal.
  
  Fig 2: Pulling Out Harness Side Connector Locking Button
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
Q: Is DTC B1631 stored?
1. YES: Go to Step 4.
2. NO: 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 knee air bag module harness side connector.
  
  Fig 3: Pulling Out Harness Side Connector Locking Button
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
3. Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991884).
4. Connect the resistor harness to the knee air bag module harness side connector.
5. Connect the negative battery terminal.
6. After erasing the DTC memory, check the DTC again.
7. Disconnect the negative battery terminal.
Q: Is DTC B1631 stored?
1. YES: Go to Step 5.
2. NO: Replace the driver's knee air bag module (Refer to SRS CONTROL UNIT (SRS-ECU) ).
  
  Fig 4: Identifying Harness Side Connector And Special Tools
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
STEP 5. Resistance check 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.
  WARNING: To release the SRS-ECU connector short spring in the following operations, disconnect this harness side connector, and keep the squib circuit shorted.
  
  Fig 5: Disconnecting SRS-ECU Connector
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
3. Use the flat-tipped screwdriver to pull out the locking button of harness side connector. After releasing the lock, disconnect the knee air bag module harness side connector.
  
  Fig 6: Pulling Out Harness Side Connector Locking Button
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  
  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.
4. Insert an insulator [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] such as cable tie between the KDS-, KDS+ line and the short spring, and release the short spring.
5. Take the measurements below at the SRS-ECU harness side connector.
  - Continuity between KDS-, KDS+ line
    OK: No continuity
    
    Fig 7: Identifying Harness Side Connector Terminals And Cable Tie
    Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
Q: Is the check result normal?
1. YES: Go to Step 6.
2. NO: Repair the wiring harness KDS-, KDS+ line between the SRS-ECU connector and the knee air bag module connector.
STEP 6. 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.
Q: Is DTC B1631 stored?
1. YES: Replace SRS-ECU (Refer to CONNECTOR ENGAGEMENT INSPECTION ).
2. NO: Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).