Code No. B1421: Right
side-airbag module (squib) system (open circuit of squib circuit)
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If diagnosis code No. B1421
is set in the SRS-ECU, be sure to diagnose the CAN bus line.
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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 and safing 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 open circuit occurs to the SRS-ECU side-airbag module (squib)
circuit.
PROBABLE CAUSES
- Open circuit to side-airbag module (squib) circuit
- Poor contact of connector
- Malfunction of SRS-ECU
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STEP 1. M.U.T.-III CAN bus diagnostics
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Use M.U.T.-III to diagnose the CAN bus lines.
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Q.
Is the check result normal?
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 Go to Step 2.
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 Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting  ).
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STEP 2. Check whether the diagnosis code is set again.
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(1)Connect the negative battery terminal.
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(2)After erasing the diagnosis code memory, check the diagnosis code again.
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(3)Disconnect the negative battery terminal.
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Q.
Is diagnosis code No. B1421 set?
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Go to Step 3.
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection
Service Points - How to Cope with Intermittent Malfunction ).
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STEP 3. Diagnosis check by dummy resistor connection
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(1)Check that the negative battery terminal is disconnected. If the negative battery
terminal is connected, disconnect it.
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(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.
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(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.
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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 diagnosis code No. B1421 set?
Go to Step 4.
Replace the front seatback pad and frame assembly (Refer to ).
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STEP 4. Resistance measurement at the SRS-ECU connector and the right
side-airbag module connector
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(1)Check that the negative battery terminal is disconnected. If the negative battery
terminal is connected, disconnect it.
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(2)Disconnect the SRS-ECU connector. <Except vehicles for Europe (double
cab) and except vehicles with ERA-GLONASS system>
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(3)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. <Vehicles for Europe (double cab) and vehicles with ERA-GLONASS system>
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(4)
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To release the connector short spring in the following operations,
disconnect this side-airbag module connector, and keep the squib circuit shorted.
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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.
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(5)
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The short spring may not be released due to the insufficient insertion, thus insert for
4 mm or more.
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Insert an insulator (width: 3 mm, thickness: 0.5 mm) such as cable tie between the SRS-,
SRS+ line and the short spring, and then release the short spring.
(6)
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Do not insert a test probe directly into the terminal
of right side-airbag module harness side connector from the connector front side as the connector
contact pressure may be weakened.
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Take the measurements below at the SRS-ECU and right side-airbag module harness side connectors.
- Continuity SRS+ line between SRS-ECU connector
and right side-airbag module connector
- Continuity SRS- line between SRS-ECU connector and right side-airbag module connector
OK: Continuity (less than 2 Ω)
Q.
Is the check result normal?
Go to Step 5.
Repair the wiring harness SRS+, SRS- line between the right side-airbag
module connector and the SRS-ECU connector.
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STEP 5. Check whether the diagnosis code is set again.
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Q.
Is diagnosis code No. B1421 set?
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Replace SRS-ECU (Refer to ).
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection
Service Points - How to Cope with Intermittent Malfunction ).
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