Code No.B1402 Driver’s air bag module (squib) system (shorted
to squib circuit earth) <Vehicles with rear curtain air
bag>
caution |
If diagnosis code B1402 is set in the
SRS-ECU, be sure to diagnose the CAN bus line.
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Only when the frontal impact
exceeding the threshold is simultaneously detected (turned
ON) by the front 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 driver’s air
bag module (squib).
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The code is set when the input
terminal of SRS-ECU driver’s air bag module (squib)
shorted to earth.
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- Damaged clock spring
- Damaged wiring harness and connectors
- Driver’s air bag module (squib) harness
shorted to earth
- 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. B1402 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/ACB04316AB00ENG.png)
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(2)Use the flat-tipped screwdriver
to pull out the locking button of wiring harness side
connector, and release the lock. (3)Connect special tool
dummy resistor (MB991865) to special tool resistor harness
(MB991866).
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![](../../../img/52/ACF01431AB00ENG.png)
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(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 (special tool) as
shown. (5)Connect the negative battery
terminal. (6)After erasing the diagnosis code memory,
check the diagnosis code again.
Q.
Is diagnosis code No. B1402 set?
Go to Step
4.
Replace
the driver’s air bag module.
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STEP 4. 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 clock spring connector.
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![](../../../img/52/ACF01432AB00ENG.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
harness side connector DQ1-, DQ1+ line. (5)Connect
the negative battery terminal. (6)After erasing the
diagnosis code memory, check the diagnosis code
again.
Q.
Is diagnosis code No. B1402 set?
Go to Step
5.
Replace
the clock spring.
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STEP 5. Resistance measurement at the SRS-ECU
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. (3)
caution |
To release SRS-ECU connector
short spring in the following operations,
disconnect this clock spring connector, and keep
the squib circuit shorted.
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Disconnect the clock spring connector.
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![](../../../img/52/AC905150BH00ENG.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 the insulator (width: 3 mm, thickness: 0.5
mm) such as cable tie between the DQ1-, DQ1+ line, and
then release the short spring. (5)Take the measurements
below at the harness side connector. Continuity between
DQ1-, DQ1+ line and body earth OK: No
continuity
Q.
Is the check result normal?
Go to Step
6.
Repair
the wiring harnesses DQ1-, DQ1+ line between the clock
spring connector and the SRS-ECU connector.
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STEP 6. Check whether the diagnosis code is set
again.
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Q.
Is diagnosis code No. B1402 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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