Code No.B1420: Side-airbag module (RH) (squib) system (short-circuited between terminals of the squib circuit)




OPERATION



  • The SRS-ECU judges how severe a collision is by detecting signals from the left and right side impact sensors. If the impact is over a predetermined level, the SRS-ECU sends an ignition signal. At this time, if the side air bag safing G-sensor is on, the SRS side-airbag will inflate.
  • The ignition signal is input to the side-airbag module to inflate the side-airbag.

DIAGNOSIS CODE SET CONDITIONS



PROBABLE CAUSES



  • Improper engaged connector or defective short spring*
  • Short circuit between the side-airbag module (RH) (squib) circuit terminals
  • Damaged connector(s)
  • Malfunction of the SRS-ECU
note *: The squib circuit connectors integrate a "short" spring (which prevents the air bag from deploying unintentionally due to static electricity by shorting the positive wire to the earth wire in the squib circuit when the connectors are disconnected).Therefore, if connector C-155 or D-36 is damaged or improperly engaged, the short spring may not be released when the connector is 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: SRS-ECU connector C-155. (M.U.T.-III diagnosis code)
(1)Disconnect the negative battery terminal.

(2)Disconnect the connectors C-155 and then reconnect them.
(3)Connect the negative battery terminal.
(4)Erase the diagnosis code memory, and check the diagnosis code.

Q. Is diagnosis code B1420 set?

Go to Step 3

The procedure is complete. It is assumed that diagnosis code B1420 set as connector C-155 was engaged improperly.

STEP 3. Connector lock check: SRS-ECU connector C-155 and side-airbag module (RH) connector D-36. (M.U.T.-III diagnosis code)
(1)Disconnect the negative battery terminal.






(2)Disconnect connectors C-155 and D-36, and then reconnect them. When disconnecting connector D-36, unlock the connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect the connector.
(3)Connect the negative battery terminal.
(4)Erase the diagnosis code memory, and check the diagnosis code.

Q. Is diagnosis code B1420 set?

Go to Step 4

The procedure is complete. It is assumed that diagnosis code B1420 set as connector C-155 or D-36 was engaged improperly.

STEP 4. Check the diagnosis code by connecting a dummy resistor. (M.U.T.-III diagnosis code)
(1)Disconnect the negative battery terminal.





(2)Disconnect side-airbag module (RH) connector D-36. When disconnecting connector D-36, unlock the connector by sliding the locking button to the direction of the arrow as shown in the figure, and then 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 the harness side connector D-36 by backprobing.
(5)Connect the negative battery terminal.
(6)Erase the diagnosis code memory, and check the diagnosis code.

Q. Is diagnosis code B1420 set?

Go to Step 5

Replace the front seatback assembly (RH) (Refer to ).

STEP 5. Resistance measurement at SRS-ECU connector C-155.
(1)Disconnect the negative battery terminal.

(2)Disconnect SRS-ECU connector C-155.





(3)
danger To prevents the air bag from deploying unintentionally, disconnect the side-airbag module (RH) connector D-36 to short the squib circuit.
Disconnect side-airbag module (RH) connector D-36. When disconnecting connector D-36, unlock the connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect the connector.

(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 53, 54 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.
Resistance measurement between C-155 harness side connector terminals 53 and 54.
OK: Open circuit

Q. Is the check result normal?

Go to Step 6

Repair the harness wires between SRS-ECU connector C-155 (terminal No.53 and 54) and side-airbag module (RH) connector D-36 (terminal No.2 and 1).

STEP 6. Check whether the diagnosis code is reset.

Q. Is diagnosis code B1420 set?
Replace the SRS-ECU (Refer to ).
An intermittent malfunction is suspected (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).