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DTC B1412: Passenger's (Front) Air Bag Module (1st squib) System (Shorted to Squib Circuit Ground)
DTC B1492: Passenger's (Front) Air Bag Module (2nd squib) System (Shorted to Squib Circuit Ground)
 
 

caution
  • If DTC B1412 <1st squib> or B1492 <2nd squib> is set in the SRS-ECU, always diagnose the CAN main bus line.
  • When DTC B1412 is set in the following diagnosis, check the 1st squib circuit. When DTC B1492 is set, check the 2nd squib circuit.
 
 
CIRCUIT OPERATION
  • The SRS-ECU judges how severe a collision is by detecting signals from the front impact sensors and the front air bag analog G-sensor. If the impact is over a predetermined level, the SRS-ECU sends an ignition signal. At this time, if the front air bag safing G-sensor is on, the SRS air bag will inflate.
  • The ignition signal is input to the air bag module to inflate the air bag.
 
 
DTC SET CONDITIONS
This DTC is set if there is abnormal resistance between the input terminals of the passenger's (front) air bag module (squib).
 
 
TROUBLESHOOTING HINTS
  • Damaged harness wires and connectors
  • Short to the ground in the passenger's (front) air bag module (squib) harness
  • Malfunction of the SRS-ECU
 
 
DIAGNOSIS
STEP 1. Using scan tool MB991958, diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
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.
Is the CAN bus line found to be normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C, 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 the "ON" position.
(3) Check if the DTC is set.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the DTC set?
Go to Step 3.
There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
 
STEP 3. Check the passenger's (front) air bag module.
(1) Disconnect the negative battery terminal.
(2) Disconnect the passenger’s (front) air bag module connector C-114.
(3) Slide the outer housing of harness side connector in the arrow direction shown, and disconnect the C-114 harness side connector.
(4) Connect special tool MB991865 to special tool MB991866.
(5)
cautionDo not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
Insert special tool MB991866 into the harness side connector C-114 (terminal No.1 and 2 <1st squib> or terminal No.3 and 4 <2nd squib>) by backprobing.
(6) Connect the negative battery terminal.
(7)
cautionAlways DTC B1B0E is set when checking DTC B1412. This is because the second side terminal is isolated when checking it. DTC B1B0E is set but this is not a fault. In addition, always DTC B1B0A is set when checking DTC B1492 because the first side terminal is isolated.
Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
Is the checked DTC set?
Go to Step 4.
Replace the passenger's (front) air bag module. (Refer to ). Then go to Step 6.
 
STEP 4. Check the passenger's (front) air bag module circuit. Measure the resistance at the SRS-ECU connector C-126.
(1) Disconnect the negative battery terminal.
(2) While pushing the part "A" indicated in the figure 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.

(3)
dangerTo prevent the air bag from deploying unintentionally, disconnect the passenger’s (front) air bag module connector C-114 to short the squib circuit.
(4) Slide the outer housing of harness side connector in the arrow direction shown, and disconnect the C-114 harness side connector.
(5)
cautionInsert an insulator such as a cable tie to a depth of 4 mm (0.16 inch) or more, otherwise the short spring will not be released.
Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminals 7 and 8 <1st squib> or 9 and 10 <2nd squib>, and the short spring to release the short spring.

(6) Check for continuity between C-126 harness side connector terminals 7 and 8 <1st squib> or 9 and 10<2nd squib>, and body ground.It should be an open circuit.
Is it open circuit?
Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1412 <1st squib> B1492 <2nd squib> sets, replace the SRS-ECU. (Refer to ). Go to Step 6.
Go to Step 5.
 
STEP 5. Check the harness wires for short circuit to ground between the following connector.
  • SRS-ECU connector C-126 (terminal No.7 and 8) and passenger's (front) air bag module connector C-114 (terminal No.1 and 2) <1st squib>.
  • SRS-ECU connector C-126 (terminal No.9 and 10) and passenger's (front) air bag module connector C-114 (terminal No.4 and 3) <2nd squib>.
Is the check result normal?
Go to Step 6.
Repair the harness wires between SRS-ECU connector C-126 and passenger's (front) air bag module connector C-114. Then go to Step 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.
Is DTC B1412 <1st squib> B1492 <2nd squib> set?
Return to Step 1.
The procedure is complete.