Code No. B1421 Right side-airbag module (squib) system (open circuit of
squib circuit) <Vehicles with rear curtain air bag>
caution |
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 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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![](../../../img/52/AC706606AC00ENG.png)
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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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![](../../../img/52/AC507310BS00ENG.png)
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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.
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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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![](../../../img/52/AC905015AC00ENG.png)
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(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 disconnect the SRS-ECU
connector.
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![](../../../img/52/AC706606AC00ENG.png)
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(3)
danger |
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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![](../../../img/52/AC905468BN00ENG.png)
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(4)
caution |
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. (5)
caution |
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.
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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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