DTC B1400: Driver's Air Bag Module (1ST Squib) System (Short Circuit Between Squib Circuit Terminals); DTC B1480: Driver's Air Bag Module (2ND Squib) System (Short Circuit Between Squib Circuit Terminals): Diagnosis

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 .
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 .
STEP 3. Check SRS-ECU connector C-126, driver's air bag module connector C-303/C-316 and clock spring connector C-313.
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. After disconnecting the C-126 SRS-ECU connector, connect it again.
3. After disconnecting C-313 clock spring, connect it again.
  
  Fig 1: Releasing Lock Lever
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
4. Disconnect the C-303/C-316 driver's air bag module connector using the flat-tipped screwdriver to pull out the locking button to the direction of the arrow, and connect it again.
5. Connect the negative battery terminal.
6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
  
  Fig 2: Pulling Out Locking Button
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  
  Q: Is DTC B1400 < 1st squib > or B1480 < 2nd squib > set?
  - YES: Go to Step 4.
  - NO: The procedure is complete. It is assumed that DTC B1400 < 1st squib > or B1480 < 2nd squib > set because connector C-126, C-303/C-316 or C-313 was engaged improperly.
STEP 4. Check the driver's air bag module.
1. Disconnect the negative battery terminal.
2. Use the flat-tipped screwdriver to pull out the locking button of wiring harness side connector, and release the lock.
  
  Fig 3: Pulling Out Locking Button
  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 resistor harness probe (special tool) as shown in the illustration.
5. Connect the negative battery terminal.
  
  Fig 4: Connecting Special Tool MB991865 To Special Tool MB991866
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  
  CAUTION: Always DTC B1481 is set when checking DTC B1400. This is because the second side terminal is isolated when checking it. DTC B1481 is set but this is not a fault. In addition, always DTC B1402 is set when checking DTC B1480 because the first side terminal is isolated.
6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
  Q: Is the checked DTC set?
  - YES: Go to Step 5.
  - NO: Replace the driver's air bag module. (Refer to DRIVER'S AIR BAG MODULE AND CLOCK SPRING . Then go to Step 8.
STEP 5. Check the clock spring.
1. Disconnect the negative battery terminal.
2. Disconnect the clock spring connector C-313.
3. Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).
  CAUTION: Do not insert a probe into the terminal from C-313 harness side connector front side directly, as the connector contact pressure may be weakened.
4. Insert the resistor harness probe from the back of C-313 harness side connector (terminal No. 3 and 4 < 1st squib > or (terminal No. 1 and 2 < 2nd squib >.
5. Connect the negative battery terminal.
  
  Fig 5: Connecting Special Tool Dummy Resistor (MB991865) To Special Tool Resistor Harness (MB991866)
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  
  CAUTION: Always DTC B1481 is set when checking DTC B1400. This is because the second side terminal is isolated when checking it. DTC B1481 is set but this is not a fault. In addition, always DTC B1401 is set when checking DTC B1480 because the first side terminal is isolated.
6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
  Q: Is the checked DTC set?
  - YES: Go to Step 6.
  - NO: Replace the clock spring. (Refer to DRIVER'S AIR BAG MODULE AND CLOCK SPRING . Then go to Step 8.
STEP 6. Check the driver's air bag module circuit. Measure the resistance at SRS-ECU connector C-126.
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-126 SRS-ECU connector.
  
  Fig 6: Releasing Lock Lever
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  
  WARNING: To prevent the air bag from deploying unintentionally, disconnect clock spring connector C-313 to short the squib circuit.
3. Disconnect clock spring connector C-313.
  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 5, 6 < 1st squib > or 3, 4 < 2nd squib > and the short spring to release the short spring.
  
  Fig 7: Identifying Cable Tie (1st Squib)
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  
  Fig 8: Identifying Cable Tie (2nd Squib)
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
5. Check for continuity between C-126 harness side connector terminals 5 and 6 < 1st squib > or 3 and 4 < 2nd squib >.
  It should be open circuit.
  
  Q: Is it open circuit?
  - YES: Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1400 < 1st squib > or B1480 < 2nd squib > set, replace the SRS-ECU. (Refer to SRS CONTROL UNIT (SRS-ECU) . Go to Step 8.
  - NO: Go to Step 7.
    
    Fig 9: Checking Continuity Between C-126 Harness Side Connector Terminals 5 And 6
    Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    
    Fig 10: Checking Continuity Between C-126 Harness Side Connector Terminals 3 And 4
    Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
STEP 7. Check the harness for short circuit between the harness wire and wire.
- SRS-ECU connector C-126 (terminal No. 5 and 6) and clock spring connector C-313 (terminal No. 3 and 4) < 1st squib >.
- SRS-ECU connector C-126 (terminal No. 3 and 4) and clock spring connector C-313 (terminal No. 1 and 2) < 2nd squib >.
  Q: the check result normal?
  - YES: Go to Step 8.
  - NO: Repair the harness wires between SRS-ECU connector C-126 and clock spring connector C-313. Then go to Step 8.
STEP 8. 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 B1400 < 1st squib > or B1480 < 2nd squib > set?
  - YES: Return to Step 1.
  - NO: The procedure is complete.