Code No.B1400: Driver’s air bag module (squib) system (short-circuited between terminals of the squib circuit)












OPERATION



TROUBLE JUDGEMENT



PROBABLE CAUSES



  • Damaged short spring *
  • Short circuit in the clock spring
  • Short circuit between the driver’s air bag module (squib) circuit terminals
  • Damaged connector(s)
  • Malfunction of the SRS-ECU
note *: The squib circuit connectors integrate a short spring (which prevents the air bags from being unintentionally deployed because of static electricity by shorting the positive wire to the earth wire in the squib circuit when the connectors are disconnected). Therefore, when the above codes are set, the short spring may not be released due to the damaged connector even when the connectors are connected.

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III diagnosis code.

Q. Is diagnosis code B1519 set?
Go to Step 2
Go to Step 3

STEP 2. Connector lock check: B-112 SRS-ECU connector.


(1)Check that the negative auxiliary battery terminal is disconnected. If the negative auxiliary battery terminal is connected, disconnect it.
(2)After disconnecting B-112 SRS-ECU connector, connect it again.
(3)Connect the negative auxiliary battery terminal.
(4)After erasing the diagnosis code memory, check the diagnosis code again.
(5)Disconnect the negative auxiliary battery terminal.

Q. Is diagnosis code B1400 set?
Go to Step 3
The procedure is complete. It is assumed that diagnosis code B1400 set as connector B-112 was engaged improperly.

STEP 3. Connector lock check: B-112 SRS-ECU connector, B-205 clock spring connector and B-207 driver’s air bag module connector.


(1)Check that the negative auxiliary battery terminal is disconnected. If the negative auxiliary battery terminal is connected, disconnect it.

(2)After disconnecting B-112 SRS-ECU, B-205 clock spring and B-207 driver’s air bag module connectors, connect them again. Disconnect B-207 driver’s air bag module connector while sliding part A shown in the figure to the direction of the arrow.
(3)Connect the negative auxiliary battery terminal.
(4)After erasing the diagnosis code memory, check the diagnosis code again.
(5)Disconnect the negative auxiliary battery terminal.

Q. Is diagnosis code B1400 set?

Go to Step 4

The procedure is complete. It is assumed that diagnosis code B1400 set as connector B-112, B-205 or B-207 was engaged improperly.

STEP 4. Check the diagnosis code by connecting a dummy resistor.


(1)Check that the negative auxiliary battery terminal is disconnected. If the negative auxiliary battery terminal is connected, disconnect it.

(2)By sliding the A section (in the figure) of the B-207 air bag module connector in the arrow direction, 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 B-207 air bag module connector by backprobing.
(5)Connect the negative auxiliary battery terminal.
(6)After erasing the diagnosis code memory, check the diagnosis code again.
(7)Disconnect the negative auxiliary battery terminal.

Q. Is diagnosis code B1400 set?

Go to Step 5

Replace the driver’s air bag module (Refer to ).

STEP 5. Check the diagnosis code by connecting a dummy resistor.


(1)Check that the negative auxiliary battery terminal is disconnected. If the negative auxiliary battery terminal is connected, disconnect it.
(2)Disconnect the B-205 clock spring 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 the B-205 clock spring harness side connector (terminal No.13 and 14) by backprobing.
(5)Connect the negative auxiliary battery terminal.
(6)After erasing the diagnosis code memory, check the diagnosis code again.
(7)Disconnect the negative auxiliary battery terminal.

Q. Is diagnosis code B1400 set?

Go to Step 6

Replace the clock spring (Refer to ).

STEP 6. Resistance measurement at the B-112 SRS-ECU connector.
(1)Check that the negative auxiliary battery terminal is disconnected. If the negative auxiliary battery terminal is connected, disconnect it.
(2)Disconnect the B-112 SRS-ECU connector.
(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 B-205 clock spring connector.

(4)
caution The short spring may not be released due to the insufficient insertion. Therefore, insert the insulator for 4 mm or more.
Insert the insulator (width: 3 mm, thickness: 0.5 mm) such as cable tie between the terminals Nos. 27 and 28, and then 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.
Take the measurements below at the B-112 harness side connector.
Continuity between terminal No. 27 and No. 28
OK: No continuity

Q. Is the check result normal?

Go to Step 7

Repair the harness wires between the B-112 SRS-ECU connector (terminal No.27 and 28) and B-205 clock spring connector (terminal No.13 and 14).

STEP 7. Check whether the diagnosis code is reset

Q. Is diagnosis code B1400 set?
Replace the SRS-ECU (Refer to ).
An intermittent malfunction is suspected (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).