Code No.B1412: Passenger’s (front) air bag module (squib) system (short-circuited to the earth)

OPERATION

The SRS-ECU judges how severe a collision is by detecting signals from the front impact sensors and the front air bag analogue 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.

DIAGNOSIS CODE SET CONDITIONS

This diagnosis code is set if the passenger’s (front) air bag squib wire(s) are short-circuited to the earth.

PROBABLE CAUSES

Damaged harness wires and connectors
Short to the earth in the passenger’s (front) air bag module (squib) harness
Malfunction of the passenger’s air bag cut off switch
Malfunction of the SRS-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check the passenger’s air bag cut off switch.

Check the passenger’s air bag cut off switch (Refer to

Q. Is the check result normal?

	Go to Step 2.

	Replace passenger’s air bag cut off switch (Refer to ).

STEP 2. Check the diagnosis code by connecting a dummy resistor. (M.U.T.-III diagnosis code)

(1)Disconnect the negative battery terminal.

(2)Disconnect passenger’s (front) air bag module connector C-02. Pull up the harness side lock lever with a nail and disconnect the connector lock.

(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 the harness side connector C-02 by backprobing.
(5)Check that the passenger’s air bag cut off switch is "ON" position.
(6)Connect the negative battery terminal.
(7)Erase the diagnosis code memory, and check the diagnosis code.

Q. Is diagnosis code B1412 set?

Go to Step 3.

Replace the passenger’s (front) air bag module (Refer to

STEP 3. Resistance measurement at the SRS-ECU connector C-154.

(1)Disconnect the negative battery terminal.

(2)Disconnect SRS-ECU connector C-154.

(3)

danger

To prevents the air bag from deploying unintentionally, disconnect the passenger’s (front) air bag module connector C-02 to short the squib circuit.

Disconnect passenger’s (front) air bag module connector C-02. Pull up the harness side lock lever with a nail and disconnect the connector lock.

(4)

caution

Insert an insulator such as a cable tie to a depth of 7 mm or more, otherwise the short spring will not be released.

Insert a cable tie [3 mm wide, 0.5 mm thick] between terminals 21, 22 and the short spring to release the short spring.
(5)Check that the passenger’s air bag cut off switch is "ON" position.

(6)

caution

Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.

Resistance measurement between C-154 harness side connector terminals 21, 22 and body earth.
OK: Open circuit

Q. Is the check result normal?

Go to Step 4.

Repair the harness wires between SRS-ECU connector C-154 (terminal No.21 and 22) and passenger’s (front) air bag module connector C-02 (terminal No.1 and 2).

STEP 4. Check whether the diagnosis code is reset.

Q. Is diagnosis code B1412 set?

	Replace the SRS-ECU (Refer to ).

	An intermittent malfunction is suspected (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).