Code No. B1431: Left
side-airbag module (squib) system (open circuit of squib circuit)
caution |
If diagnosis code No. B1431
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. B1431 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 left 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/AC507310BT00ENG.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 left 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. B1431 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 left
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.
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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 left 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/ACE02056AM00ENG.png)
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(4)
caution |
The short spring may not be released due to the
insufficient insertion. Therefore, insert
the insulator 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 SLS-,
SLS+ line and the short spring, and then release the short
spring. (5)
caution |
Do not insert a test probe directly into the
terminal
of left 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 left impact sensor
harness side connectors.
- Continuity SLS- line between SRS-ECU connector and left
side-airbag module connector
- Continuity SLS+ line between SRS-ECU connector and left
side-airbag module
connector
OK: Continuity (less than 2 Ω)
Q.
Is the check result normal?
Go to Step 5.
Repair the wiring harness SLS-,
SLS+ line between the left 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. B1431 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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