DTC B1401: Driver's Air Bag Module (1st Squib) System Fault 2 (Open in the Squib Circuit) : DTC B1481: Driver's Air Bag Module (2nd Squib) System Fault 2 (Open in the Squib Circuit): Diagnosis

Required Special Tools:

MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A
MB991865: Dummy resistor
MB991866: Resister harness

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 Scan Tool To Data Link Connector
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
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 COPE WITH INTERMITTENT MALFUNCTIONS ).

Fig 2: Connecting Scan Tool To Data Link Connector
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
STEP 3. Check the driver's air bag module. (Using scan tool MB991958, read the diagnostic trouble code.)
1. Disconnect the negative battery terminal.
2. Slide the outer housing of the driver' s air bag module connector C-305 in the arrow direction shown, and disconnect the connector.
  
  Fig 3: Identifying Connector C-305 Terminals
  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 clock spring side of driver's air bag module connector C-305 (terminal No.1 and 2 < 1st squib > or terminal No.3 and 4 < 2nd squib >) by backprobing.
5. Connect the negative battery terminal.
6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
  
  Fig 4: Checking Driver's Air Bag Module
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
Q: Is DTC B1401 < 1st squib > or B1481 < 2nd squib > set?

YES: Go to Step 4.

NO: Replace the driver's air bag module (Refer to AIR BAG MODULES AND CLOCK SPRING ). Then go to Step 6.
STEP 4. Check the clock spring. (Using scan tool MB991958, read the diagnostic trouble code.)
1. Disconnect the negative battery terminal.
2. Disconnect the clock spring connector C-307.
  
  Fig 5: Identifying Connector C-307 Terminals
  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 harness side of clock spring connector C-307 (terminal No.13 and 14 < 1st squib > or terminal No.11 and 12 < 2nd squib >) by backprobing.
5. Connect the negative battery terminal.
6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
Q: Is DTC B1401 < 1st squib > or B1481 < 2nd squib > set?

Fig 6: Checking Clock Spring Connector C-307
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

YES: Go to Step 5.

NO: Replace the clock spring (Refer to AIR BAG MODULES AND CLOCK SPRING ). Then go to Step 6.
STEP 5. Check the harness between the SRS-ECU connector C-121 (terminal No.36 and 37 < 1st squib > or terminal No.33 and 34 < 2nd squib >) and the clock spring connector C-307 (terminal No.13 and 14 < 1st squib > or terminal No.11 and 12 < 2nd squib >) for open circuit.
1. Disconnect SRS-ECU connector C-121 and clock spring connector C-307.
  
  Fig 7: Identifying Connector C-121 Terminals
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  
  Fig 8: Identifying Connector C-307 Terminals
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  
  CAUTION: Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
2. Check for continuity between the following terminals. It should be less than 2 ohms.
  < 1st squib >
  - SRS-ECU connector C-121 (terminal No.36) and the clock spring connector C-307 (terminal No.13)
  - SRS-ECU connector C-121 (terminal No.37) and the clock spring connector C-307 (terminal No.14)
    
    Fig 9: Checking Continuity Between Terminals (1 Of 2)
    Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  < 2nd squib >
  - SRS-ECU connector C-121 (terminal No.33) and the clock spring connector C-307 (terminal No.11)
  - SRS-ECU connector C-121 (terminal No.34) and the clock spring connector C-307 (terminal No.12)
Q: Does continuity exist?

YES: Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1401 < 1st squib > or B1481 < 2nd squib > set, replace the SRS-ECU (Refer to SRS CONTROL UNIT (SRS-ECU) ). Then go to Step 6.

NO: Replace the harness wires between SRS-ECU connector C-121, intermediate connector C-22 and clock spring connector C-307. Then go to Step 6.

Fig 10: Checking Continuity Between Terminals (2 Of 2)
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
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 B1401 < 1st squib > or B1481 < 2nd squib > set?

YES: Return to Step 1.

NO: The procedure is complete.

Fig 11: Connecting Scan Tool To Data Link Connector
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.