Code No.1402: Driver’s air bag (1st squib) (earth side) short-circuited
Code No.1482: Driver’s air bag (2nd squib) (earth side) short-circuited












caution If diagnosis code B1402 <1st squib> or B1482 <2nd squib> is set in the SRS-ECU, always diagnose the CAN main bus line.

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 sent to the air bag module via the clock spring to inflate the air bag.

DIAGNOSIS CODE SET CONDITIONS



PROBABLE CAUSES



  • Malfunction of the clock spring
  • Damaged harness wires and connectors
  • Short to the earth in the driver’s air bag module (squib) harness
  • Malfunction of the SRS-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54D, Diagnosis ).

STEP 2. Check whether the diagnosis code is reset.
Check again if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Ignition: "LOCK" (OFF) position to "ON"
(3)On completion, check that the diagnosis code is not reset.

Q. Is the diagnosis code 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 driver’s air bag module.
(1)Disconnect the negative battery terminal.

(2)Slide the outer housing of the driver’ s air bag module connector D-304 in the arrow direction shown, and disconnect the connector.

(3)Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).
(4)
caution Do 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 clock spring side air bag module connector D-304 (terminal No.1 and 2 <1st squib> or terminal No.3 and 4 <2nd squib>) by backprobing.
(5)Connect the negative battery terminal.
(6)
caution Always diagnosis code B1481 is set when checking diagnosis code B1402. This is because the second side terminal is isolated when checking it, diagnosis code B1481 is set but this is not a fault. In addition, always diagnosis code B1401 is set when checking diagnosis code B1482 because the first side terminal is isolated.
Erase the diagnosis code from memory, and check the diagnosis code.

Q. Is the checked diagnosis code set?

Go to Step 4.

Replace the driver’s air bag module (Refer to ). Then go to Step 7.

STEP 4. Check the clock spring.
(1)Disconnect the negative battery terminal.
(2)Disconnect the clock spring connector D-306.

(3)Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).
(4)
caution Do 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 clock spring harness side connector D-306 (terminal No.3 and 4 <1st squib> or terminal No.1 and 2 <2nd squib>) by backprobing.
(5)Connect the negative battery terminal.
(6)
caution Always diagnosis code B1481 is set when checking diagnosis code B1402. This is because the second side terminal is isolated when checking it, diagnosis code B1481 is set but this is not a fault. In addition, always diagnosis code B1401 is set when checking diagnosis code B1482 because the first side terminal is isolated.
Erase the diagnosis code from memory, and check the diagnosis code.

Q. Is the checked diagnosis code set?

Go to Step 5.

Replace the clock spring (Refer to ). Then go to Step 7.

STEP 5. Check the driver’s air bag module circuit. Resistance measurement at the SRS-ECU connector D-24.
(1)Disconnect the negative battery terminal.
(2)Disconnect SRS-ECU connector D-24.
(3)
danger To release SRS-ECU connector short spring in the following operations, disconnect this clock spring connector, and keep the squib circuit shorted.
Disconnect the clock spring connector D-306.


(4)
caution Insert an insulator such as a cable tie to a depth of 4 mm or more, otherwise the short spring will not be released.
Insert a cable tie [3 mm wide, 0.5 mm thick] between terminals 36, 37 <1st squib> or 33, 34 <2nd squib> and the short spring to release the short spring.
(5)
caution Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
Check for continuity between D-24 (harness side connector terminals 36 and 37 <1st squib> or 33 and 34 <2nd squib>) and body earth.
OK: Open circuit

Q. Is the check result normal?

Erase the diagnosis code from memory, and check the diagnosis code. If diagnosis code B1402 <1st squib> or B1482 <2nd squib> sets, replace the SRS-ECU (Refer to ). Then go to Step 7.

Go to Step 6.

STEP 6. Check the harness for short circuit to earth between SRS-ECU connector D-24 (terminal No.36 and 37 <1st squib> or terminal No.33 and 34 <2nd squib>) and clock spring connector D-306 (terminal No.3 and 4 <1st squib> or terminal No.1 and 2 <2nd squib>).

Q. Are the harness wires between SRS-ECU connector D-24 (terminal No.36 and 37 <1st squib> or terminal No.33 and 34 <2nd squib>) and clock spring connector D-306 (terminal No.3 and 4 <1st squib> or terminal No.1 and 2 <2nd squib>) in good condition?
Go to Step 7.
Replace the harness wires between SRS-ECU connector D-24 and clock spring connector D-306. Then go to Step 7.

STEP 7. Check whether the diagnosis code is reset.


Q. Is diagnosis code B1402 <1st squib> or B1482 <2nd squib> set?
Return to Step 1.
The procedure is complete.