Code No.B1420 Right side-airbag module (squib) system (short circuit between squib terminals)


caution If the diagnosis code B1420 is set to SRS-ECU, be sure to diagnose the CAN bus line.

OPERATION


In case of side collision, when the impact exceeding the threshold is applied to the vehicle, and when the impact is simultaneously detected (turned ON) by the side impact sensor as well as by the analogue G-sensor in SRS-ECU, the electric current is supplied from SRS-ECU to the side-airbag module (squib) of impacted side.

TROUBLE JUDGEMENT


The code is set when the short circuit occurs to between the terminals of SRS-ECU side-airbag module (squib) circuit.

PROBABLE CAUSES



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 CAN bus diagnostics.
Use 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 54C - Troubleshooting ).

STEP 2. Check whether the diagnosis code is reset.
(1)Connect the negative battery terminal.
(2)After erasing the diagnosis code memory, check the diagnosis code again.
(3)Disconnect the negative battery terminal.

Q. Is the diagnosis code No. B1420 set?
Go to Step 3.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).

STEP 3. Connector check: SRS-ECU, right side-airbag module.
(1)Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.

(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. After disconnecting the SRS-ECU connector, connect it again.

(3)After disconnecting the right side-airbag module connector, connect the connector again. For the right side-airbag module connector disconnection, 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)Connect the negative battery terminal.
(5)After erasing the diagnosis code memory, check the diagnosis code again.
(6)Disconnect the negative battery terminal.

Q. Is the diagnosis code No. B1420 set?

Go to Step 4.

Replace the connector concerned.

STEP 4. Diagnosis check by dummy resistor connection.
(1)Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.

(2)Disconnect the right side-airbag module connector, 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 probe directly into the terminal from the connector front side as the connector contact pressure may be weakened.
Insert the resistor harness probe from the back of right side-airbag module harness side connector.
(5)Connect the negative battery terminal.
(6)After erasing the diagnosis code memory, check the diagnosis code again.
(7)Disconnect the negative battery terminal.

Q. Is the diagnosis code No. B1420 set?

Go to Step 5.

Replace the front seatback pad and frame assembly (Refer to ).

STEP 5. Resistance measurement at the SRS-ECU connector.
(1)Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.

(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 SRS-ECU connector.

(3)
danger To release the connector short spring in the following operations, disconnect this side-airbag module connector, and keep the squib circuit shorted.
Disconnect the right side-airbag module connector, 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 The short spring may not be released due to the insufficient insertion, thus insert for 4 mm or more.
Insert a cable tie (width: 3 mm, thickness: 0.5 mm) between the SRS+, SRS- line and the short spring, and then release the short spring.
(5)Take the measurements below at the right side-airbag module harness side connector.

  • Continuity between SRS+, SRS- line
OK: No continuity

Q. Is the check result normal?

Go to Step 6.

Repair the wiring harness SRS+, SRS- line between the right side-airbag module connector and the SRS-ECU connector.

STEP 6. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No. B1420 set?
Replace SRS-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).