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Home >> Mitsubishi >> 2014 >> Lancer SE >> Repair and Diagnosis >> External Pages >> Different car >> Section 37 (Supplemental Restraint System (SRS) - With Diagnostics) >> SRS Air Bag Diagnosis >> Diagnostic Trouble Code Procedures >> DTC B1421: Side-airbag module (RH) (squib) system (open circuit of squib circuit) >> Diagnosis

DTC B1421: Side-airbag module (RH) (squib) system (open circuit of squib circuit): 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.
  1. 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 "ON" position.
    3. Diagnose the CAN bus line.
    4. Turn the ignition switch to the "LOCK" (OFF) position.

    Q: Is the check result satisfactory? 

    1. YES:  Go to Step 2.
    2. NO:  Repair the CAN bus line (Refer to DIAGNOSIS ).
  2. 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:  Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
  3. STEP 3. Check the side-airbag module (RH). 
    1. Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
    2. Disconnect the side-airbag module (RH) connector, unlock the connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect the connector.
      Fig 1: Disconnecting Side-Airbag Module Connector
      G09666542Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    3. Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).
      CAUTION: Do not insert a probe directly into the terminal from the connector front side as the connector contact pressure may be weakened.
    4. Insert the resistor harness probe from the back of side-airbag module (RH) harness side connector.
    5. Connect the negative battery terminal.
    6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
    7. Disconnect the negative battery terminal.
      Fig 2: Identifying Side Airbag Module Connector And Special Tools
      G09666543Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is DTC B1421 stored? 

    1. YES:  Go to Step 4.
    2. NO:  Replace the front seatback pad and frame assembly (Refer to SIDE-AIRBAG MODULE(S)  ).
  4. STEP 4. Resistance measurement at the SRS-ECU connector and the side-airbag module (RH) 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 connector short spring in the following operations, disconnect this side-airbag module connector, and keep the squib circuit shorted.
      Fig 3: Disconnecting SRS-ECU Connector
      G09666544Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    3. Disconnect the side-airbag module (RH) connector, unlock the connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect the connector.
      Fig 4: Disconnecting Side-Airbag Module Connector
      G09666545Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      CAUTION: The short spring may not be released due to the insufficient insertion, thus insert for 4 mm (0.16 inch) or more.
    4. Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between the SRS+, SRS- line and the short spring, and then release the short spring.
      CAUTION: Do not insert a test probe directly into the terminal of side-airbag module (RH) harness side connector from the connector front side as the connector contact pressure may be weakened.
      Fig 5: Identifying Harness Side Connector And Cable Tie
      G09666546Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    5. Take the measurements below at the SRS-ECU and side-airbag module (RH) harness side connectors.
      • Continuity SRS+ line between SRS-ECU connector and side-airbag module (RH) connector
      • Continuity SRS- line between SRS-ECU connector and side-airbag module (RH) connector

        OK: Continuity (less than 2 Ω) 

    Q: Is the check result normal? 

    1. YES:  Go to Step 5.
    2. NO:  Repair the wiring harness SRS+, SRS- line between the side-airbag module (RH) connector and the SRS-ECU connector.
  5. 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.

    Q: Is DTC B1421 stored? 

    1. YES:  Replace SRS-ECU (Refer to SRS CONTROL UNIT (SRS-ECU)  ).
    2. NO:  Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
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