DTC B1B1A: Curtain Air Bag Module (LH) (Squib) System (Squib Circuit Open): 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
• MB991884: 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 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? 

   • 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 MALFUNCTIONS ).
3. STEP 3. Check by dummy resistor connection. 
   1. Disconnect the negative battery terminal.
   2. Disconnect the D-12 intermediate 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 D-12 Intermediate Connector Unlock Connector

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   3. Connect special tool MB991865 to special tool MB991866.
      CAUTION: Do not insert a probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
   4. Insert the probe of resistor harness, to which the dummy resistor is installed, from the back of D-12 intermediate connector (floor harness side).
   5. Connect the negative battery terminal.
   6. After erasing the diagnostic trouble code memory, check the diagnostic trouble code again.
   7. Disconnect the negative battery terminal.

   Q: Is DTC B1B1A set? 

   • YES:  Go to Step 4.
   • NO:  Go to  Step 5.
     Fig 3: Connecting Special Tool MB991865 To Special Tool MB991866

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
4. STEP 4. Resistance measurement at the C-30 SRS-ECU connector and the D-12 intermediate connector. 
   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.
      WARNING: To release the SRS-ECU connector short spring in the following operations, disconnect this intermediate connector, and keep the squib circuit shorted.
   3. Disconnect the D-12 intermediate 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 4: Turning Lock Lever

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      Fig 5: Disconnecting D-12 Intermediate Connector Unlock Connector

      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 (0.6 inch) or more.
   4. Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminal 41, 42 and the short spring to release the short spring.
      Fig 6: Inserting Cable Tie Wide Thick Between Terminal 41, 42 And Short Spring

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      CAUTION: Do not insert a probe into the terminal from D-12 intermediate connector front side directly, as the connector contact pressure may be weakened.
   5. Check for continuity between the following terminals. It should be less than 2 ohms.
      • SRS-ECU connector C-30 (terminal No. 41) and the intermediate connector D-12 (terminal No. 1)
      • SRS-ECU connector C-30 (terminal No. 42) and the intermediate connector D-12 (terminal No. 2)

   Q: Does continuity exist? 

   • YES:  Go to  Step 6.
   • NO:  Repair the wiring harness between the C-30 harness side connector terminal No. 41, 42 and the D-12 intermediate connector (floor harness side) terminal No. 1, 2.
     Fig 7: Checking Continuity Between SRS-ECU Connector C-30 (Terminal 41) And Intermediate Connector D-12 (Terminal 1)

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
5. STEP 5. Resistance measurement at the D-12 intermediate connector terminal No. 1, 2 and the F-24 curtain air bag module harness side connector terminal No. 1, 2. 
   1. Disconnect the negative battery terminal.
   2. Disconnect curtain air bag module (LH) F-24. Use a flat-tipped screwdriver to unlock the locking button at the harness side connector by withdrawing it toward you in two stages, and then disconnect the connector.
      Fig 8: Disconnecting Curtain Air Bag Wiring Harness Connector

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   3. Disconnect the D-12 intermediate 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 9: Disconnecting D-12 Intermediate Connector Unlock Connector

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   4. Because the short spring is installed to the D-12 intermediate connector (curtain air bag harness side), insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminals 1, 2 and the short spring to release the short spring.
      Fig 10: Inserting Cable Tie Wide Thick Between Terminals 1, 2 And Short Spring

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   5. Connect special tool MB991884 to the removed F-24 harness side connector.
      Fig 11: Connecting Special Tool MB991884 To F-24 Harness Side Connector

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      CAUTION: Do not insert a probe into the terminal from D-12 intermediate connector front side directly, as the connector contact pressure may be weakened.
   6. Check for continuity between the following terminals. It should be less than 2 ohms.
      • Intermediate connector D-12 (terminal No. 1) and resistor harness connector terminal No. 2)
      • Intermediate connector D-12 (terminal No. 2) and resistor harness connector terminal No. 1)

   Q: Does continuity exist? 

   • YES:  Replace the curtain air bag module (LH) (Refer to CURTAIN AIR BAG MODULE(S)  ).
   • NO:  Repair the wiring harness.
     Fig 12: Checking Continuity Between Intermediate Connector D-12 Terminal 1 And Resistor Harness Connector Terminal 2

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
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 B1B1A set? 

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