Code No. B1420: Right
side-airbag module (squib) system (short circuit between squib
terminals)
caution |
If diagnosis code No. B1420
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 short circuit
occurs to between the terminals of SRS-ECU side-airbag module
(squib) circuit.
PROBABLE CAUSES
- Damaged short spring *
- Short circuit between terminals of side-airbag module (squib)
circuit
- Damaged connector(s)
- Malfunction of SRS-ECU
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. B1420 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, right side-airbag
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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(2)After disconnecting the SRS-ECU connector,
connect it again.
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![](../../../img/52/AC706606AC00ENG.png)
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(3)After disconnecting the right
side-airbag module connector, connect the connector again.
For the right side-airbag module connector disconnection,
unlock the connector by sliding the
locking button to the direction of the arrow as shown in the
figure, and then disconnect the
connector. (4)Connect the negative battery
terminal. (5)After erasing the diagnosis code memory,
check the diagnosis code again. (6)Disconnect the
negative battery terminal.
Q.
Is diagnosis code No. B1420 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/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. B1420 set?
Go to Step
5.
Replace
the front seatback pad and frame assembly.
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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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(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 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/ACE02056AL00ENG.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 a cable tie (width: 3 mm, thickness: 0.5 mm)
between the SRS+, SRS- line
and the short spring, and then release the short
spring. (5)Take the measurements below at the right
side-airbag module harness side connector.
- Continuity between SRS+, SRS- line
OK: No continuity
Q.
Is the check result normal?
Go to Step
6.
Repair
the wiring harness SRS+, SRS- line between the right
side-airbag
module 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. B1420 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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