DTC B1C28: Side-airbag Module (LH) (Squib) System (Shorted to Squib Circuit Power Supply): 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

1. 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  ."
   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? 

   • YES:  Go to Step 2.
   • NO:  Repair the CAN bus line (Refer to DIAGNOSIS ).
     Fig 1: Connecting Special Tool MB991910 To Data Link Connector

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
2. 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 (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
3. STEP 3. Check the side-airbag module (LH). 
   1. Disconnect the negative battery terminal.
   2. Disconnect the D-30 side-airbag module connector, unlock the connector by sliding the locking button to the direction of the arrow as shown in the illustration , and then disconnect the connector.
      Fig 2: Disconnecting Side-Airbag Module Connector

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   3. Connect special tool MB991865 to special tool MB991866.
      CAUTION: Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
   4. Insert special tool MB991866 into the D-30 harness side connector by backprobing.
   5. Connect the negative battery terminal.
   6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

   Q: Is DTC B1C28 set? 

   • YES:  Go to Step 4.
   • NO:  Replace the front seatback assembly (Refer to DISASSEMBLY AND ASSEMBLY ) < Except RALLIART >, or replace the front seatback (Refer to DISASSEMBLY AND ASSEMBLY ) < RALLIART >. Then go to  Step 6.
     Fig 3: Connecting Special Tool MB991865 To Special Tool MB991866

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
4. STEP 4. Check the side-airbag module (LH) circuit. Measure the voltage at the SRS-ECU connector C-30. 
   1. Disconnect the negative battery terminal.
   2. While pushing the part "A" indicated in the illustration of the harness side connector, turn the lock lever to the direction of the arrow to release the lock lever, and disconnect the C-30 SRS-ECU connector.
      Fig 4: Turning Lock Lever

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      WARNING: To prevent the air bag from deploying unintentionally, disconnect the side-airbag module (LH) connector D-30 to short the squib circuit.
   3. Disconnect the D-30 side-airbag module connector, unlock the connector by sliding the locking button to the direction of the arrow as shown in the illustration , and then disconnect the connector.
      Fig 5: Disconnecting Side-Airbag Module Connector

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      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.
   4. 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. Connect the negative battery terminal.
   6. Ignition switch: "ON".
      Fig 6: Inserting Cable Tie Wide Thick Between Terminals 31, 32 And Short Spring

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   7. Measure the voltage between C-30 harness side connector terminals 31, 32 and body ground. Voltage should measure 1 volt or less.

   Q: Is the measured voltage within the specified range? 

   • YES:  Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1C28 sets, replace the SRS-ECU (Refer to SRS CONTROL UNIT (SRS-ECU)  ). Then go to  Step 6.
   • NO:  Go to Step 5.
     Fig 7: Measuring Voltage Between C-30 Harness Side Connector Terminals 31, 32 And Body Ground

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
5. STEP 5. Check the harness wires for short circuit to power supply between SRS-ECU connector C-30 (terminal No. 31 and 32 and side-airbag module (LH) connector D-30 (terminal No. 2 and 1). 

   Q: Is the check result normal? 

   • YES:  Go to Step 6.
   • NO:  Repair the harness wires between SRS-ECU connector C-30 and side-airbag module (LH) connector D-30. Then go to Step 6.
6. 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.

   Q: Is DTC B1C28 set? 

   • YES:  Return to  Step 1.
   • NO:  The procedure is complete.