DTC B1411: Passenger's (Front) Air Bag Module (1st Squib) System Fault 2 (Open in the Squib Circuit); DTC B1491: Passenger's (Front) Air Bag Module (2nd Squib) System Fault 2 (Open in the Squib Circuit): Diagnosis

Required Special Tools: 

• MB991958: Scan Tool (MUT-III Sub Assembly)
  • MB991824: V.C.I.
  • MB991827: MUT-III USB Cable
  • MB991910: MUT-III Main Harness A
• MB991865: Dummy resister
• 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 (MUT-III)  ."
   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 Scan Tool To Data Link Connector

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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 the "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 Use Troubleshooting/Inspection Service Points - HOW TO COPE WITH INTERMITTENT MALFUNCTIONS ).

   Fig 2: Connecting Scan Tool To Data Link Connector

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3. STEP 3. Check the passenger's air bag module. (Using scan tool MB991958, read the diagnostic trouble code.) 
   1. Disconnect the negative battery terminal.
   2. Disconnect the passenger's air bag module connector C-112.
      Fig 3: Identifying Connector C-112 Terminals

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   3. Slide the outer housing of passenger's air bag module connector C-112 in the arrow direction shown in illustration, and disconnect the connector.
      Fig 4: Disconnecting Passenger's Air Bag Module Connector C-112

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   4. 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.
   5. Insert special tool MB991866 into the harness side connector C-112 (terminal No.1 and 2 < 1st squib > or terminal No. 3 and 4 < 2nd squib >) by backprobing.
   6. Connect the negative battery terminal.
   7. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
      Fig 5: Inserting Special Tool MB991866 Into Harness Side Connector C-112

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   Q: Is DTC B1411 < 1st squib > or B1491 < 2nd squib > set? 

   YES :  Go to Step 4.

   NO :  Replace the passenger's air bag module (Refer to AIR BAG MODULE(S) AND CLOCK SPRING  ). Then go to  Step 5.

4. STEP 4. Check the harness for open circuit between SRS-ECU connector C-123 (terminal No. 27 and 28 < 1st squib > or terminal No. 30 and 31 < 2nd squib >) and the passenger's air bag module connector C-112 (terminal No. 1 and 2 < 1st squib > or terminal No. 4 and 3 < 2nd squib >). 
   1. Unclip passenger's air bag module connector C-112.
      Fig 6: Locating Passenger's Air Bag Module Connector C-112

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   2. Disconnect SRS-ECU connector C-123 and passenger's air bag module connector C-112.
      Fig 7: Disconnecting Connector C-123 Terminals

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      CAUTION: Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
   3. Check for continuity between the following terminals. It should be less than 2 ohms.
      Fig 8: Checking Continuity Between SRS-ECU Connector C-123 And Passenger's Air Bag Module Connector (1st Squib)

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      < 1st squib > 

      • SRS-ECU connector C-123 (terminal No. 27) and the passenger's air bag module connector C-112 (terminal No. 1)
      • SRS-ECU connector C-123 (terminal No. 28) and the passenger's air bag module connector C-112 (terminal No. 2)

      < 2nd squib > 

      • SRS-ECU connector C-123 (terminal No. 30) and the passenger's air bag module connector C-112 (terminal No. 4)
      • SRS-ECU connector C-123 (terminal No. 31) and the passenger's air bag module connector C-112 (terminal No. 3)

   Q: Does continuity exist? 

   YES :  Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1411 < 1st squib > or B1491 < 2nd squib > set, replace the SRS-ECU (Refer to SRS CONTROL UNIT (SRS-ECU)  ). Then go to Step 5.

   Fig 9: Checking Continuity Between SRS-ECU Connector C-123 And Passenger's Air Bag Module Connector (2nd Squib)

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   NO :  Replace the harness wires between SRS-ECU connector C-123 and passenger's air bag module connector C-112. Then go to Step 5.

5. STEP 5. 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 B1411 < 1st squib > or B1491 < 2nd squib > set? 

   YES :  Return to  Step 1.

   NO :  The procedure is complete.

   Fig 10: Connecting Scan Tool To Data Link Connector

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.