Code No.B1400 Driver’s air bag module (squib) system (short
circuit between squib circuit terminals) <Vehicles with rear
curtain air bag>
caution |
- If diagnosis code No. B1400 (squib) 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 short
circuit occurs to between the terminals of SRS-ECU
driver’s air bag module (squib) circuit.
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- Damaged short spring *
- Short circuit in the clock spring
- Short circuit between terminals of driver’s
air bag module (squib) circuit
- Damaged connector(s)
- Malfunction of SRS-ECU
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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.
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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. B1400 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. Connector check: SRS-ECU, clock spring,
driver’s air bag module.
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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 disconnecting the SRS-ECU connector,
connect it again. (3)After disconnecting clock spring,
connect it again.
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![](../../../img/52/ACB04316AB00ENG.png)
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(4)Disconnect the driver’s
air bag module connector using the slotted (-) screwdriver
to pull out the locking button to the direction of the
arrow, and connect it again. (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. B1400 set?
Go to Step
4.
Replace
the connector concerned.
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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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![](../../../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. (7)Disconnect the
negative battery terminal.
Q.
Is diagnosis code No. B1400 set?
Go to Step
5.
Replace
the driver’s air bag module.
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STEP 5. 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. (7)Disconnect the negative battery
terminal.
Q.
Is diagnosis code No. B1400 set?
Go to Step
6.
Replace
the clock spring.
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STEP 6. 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 OK: No
continuity
Q.
Is the check result normal?
Go to Step
7.
Repair
the wiring harnesses DQ1-, DQ1+ line between the clock
spring connector and the SRS-ECU connector.
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STEP 7. Check whether the diagnosis code is set
again.
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Q.
Is diagnosis code No. B1400 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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