Code No.B1400: Driver’s Air Bag Module (1st Squib) System
Fault 1 (Short Circuit between Terminals of the Squib
Circuit)
![](../../../img/52/W4X52X001A00ENG.png)
caution |
If diagnosis code B1400 <1st
squib> or B1480 <2nd squib> is set in the
SRS-ECU, always diagnose the CAN bus lines.
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OPERATION
- The SRS-ECU judges how severe a collision is by detecting
signals from the front impact sensors and the front air bag
analogue G-sensor. If the impact is over a predetermined level,
the SRS-ECU sends an ignition signal. At this time, if the front
air bag safing G-sensor is on, the SRS air bag will inflate.
- The ignition signal is input to the air bag module via the clock
spring to inflate the air bag.
DIAGNOSIS CODE SET CONDITIONS
- This diagnosis code is set if there is abnormal resistance
between the input terminals of the driver’s side air bag
module (squib). The most likely causes for this code to be set
are the followings:
- Short circuit in driver’s air bag module
(squib) or harness
- Short circuit in the clock spring
PROBABLE CAUSES
- Improper engaged connector or defective short
spring*
- Short circuit in the clock spring
- Short circuit between the driver’s air bag module (squib)
circuit terminals
- Damaged connector(s)
- Malfunction of the SRS-ECU
note |
*: The squib circuit connectors
integrate a "short" spring (which prevents the air bag from
deploying unintentionally due to static electricity by
shorting the positive wire to the earth wire in the squib
circuit when the connectors are disconnected). (Refer to ).
Therefore, if connector C-119, C-309 or C-312 is damaged or
improperly engaged, the short spring may not be released
when the connector is connected.
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STEP 1. M.U.T.-III CAN bus diagnostics
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Use the 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 54F, Diagnosis ).
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STEP 2. Check whether the diagnosis code is
reset.
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Check again if the diagnosis code
is set.
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(1)Erase the diagnosis code.
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(2)Ignition: LOCK (OFF) position to ON
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(3)On completion, check that the diagnosis code is
not reset.
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Q.
Is the diagnosis code set?
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Go to Step 3
.
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There is an
intermittent malfunction such as poor engaged connector(s)
or open circuit (Refer to GROUP 00, How to Cope with
Intermittent Malfunction ).
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STEP 3. M.U.T.-III diagnosis code
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caution |
To prevent damage to
M.U.T.-III, always turn the ignition switch to
the "LOCK" (OFF) position before connecting or
disconnecting M.U.T.-III.
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(1)Turn the ignition switch to the "ON"
position.
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(2)Check if the diagnosis code is set.
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(3)Turn the ignition switch to the "LOOK" (OFF)
position.
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Q.
Is diagnosis code B1519 set?
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Go to Step 4
.
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Go to Step 5
.
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STEP 4. Connector check: SRS-ECU connector
C-119.
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![](../../../img/52/AC311438AD00ENG.png)
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Q.
Is the connector correctly engaged?
Go to Step 5
.
Engage the
connector correctly. Then go to Step 10.
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STEP 5. Connector check: SRS-ECU connector C-119, clock
spring connector C-309 and driver’s air bag module
connector C-312 (M.U.T.-III diagnosis
code.)
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(1)Disconnect the negative battery
terminal.
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![](../../../img/52/AC311438AD00ENG.png)
![](../../../img/52/AC313402AC00ENG.png)
![](../../../img/52/AC313412AC00ENG.png)
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(2)Disconnect connectors C-119,
C-309 and C-312, and then reconnect them. (3)Connect the
negative battery terminal. (4)Erase the diagnosis trouble
code memory, and check the diagnosis trouble code.
Q.
Is diagnosis code B1400 set?
Go to Step 6
.
The
procedure is complete. It is assumed that diagnosis code
B1400 set because connector C-119, C-309 or C-312 was
engaged improperly.
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STEP 6. Check the driver’s air bag module
(M.U.T.-III diagnosis code).
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(1)Disconnect the negative battery
terminal.
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![](../../../img/52/AC302435AG00ENG.png)
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(2)Slide the outer housing of the
clock spring side of driver’s air bag module connector
C-312 in the arrow direction shown, and disconnect the
connector.
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![](../../../img/52/AC303006AE00ENG.png)
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(3)Connect special tool dummy
resistor (MB991865) to special tool resistor harness
(MB991866). (4)
caution |
Do not insert a test probe
into the terminal from its front side directly
as the connector contact pressure may be
weakened.
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Insert special tool MB991866 into clock spring side
of driver’s air bag module connector C-312 (terminal
No.1 and 2) by backprobing. (5)Connect the negative
battery terminal. (6)Erase the diagnosis code memory, and
check the diagnosis code.
Q.
Is the checked diagnosis code set?
Go to Step 7
.
Replace the
driver’s air bag module (Refer to ). Then go
to Step 10 .
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STEP 7. Check the clock spring (M.U.T.-III diagnosis
code).
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(1)Disconnect the negative battery
terminal.
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![](../../../img/52/AC313402AD00ENG.png)
![](../../../img/52/AC313412AE00ENG.png)
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(2)Disconnect the clock spring
connector C-309.
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![](../../../img/52/AC306767AC00ENG.png)
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(3)Connect special tool dummy
resistor (MB991865) to special tool resistor harness
(MB991866). (4)
caution |
Do not insert a test probe
into the terminal from its front side directly,
as the connector contact pressure may be
weakened.
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Insert special tool MB991866 into clock spring
harness side connector C-309 (terminal No.3 and 4) by
backprobing. (5)Connect the negative battery
terminal. (6)Erase the diagnosis code memory, and check
the diagnosis code.
Q.
Is the checked diagnosis code set?
Go to Step 8
.
Replace the
clock spring (Refer to ). Then go
to Step 10 .
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STEP 8. Check the driver’s air bag module circuit.
Resistance measurement at SRS-ECU connector
C-119.
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![](../../../img/52/AC311438AD00ENG.png)
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(1)Disconnect SRS-ECU connector
C-119.
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![](../../../img/52/AC313402AD00ENG.png)
![](../../../img/52/AC313412AE00ENG.png)
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(2)
danger |
To prevent the air bag from
deploying unintentionally, disconnect clock
spring connector C-309 to short the squib
circuit.
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Disconnect clock spring connector C-309.
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![](../../../img/52/AC308144AE00ENG.png)
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(3)
caution |
Insert an insulator such as a
cable tie to a depth of 4mm or more, otherwise
the short spring will not be released.
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Insert a cable tie [3 mm wide, 0.5 mm
thick] between terminals 36, 37 and the short spring
to release the short spring.
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![](../../../img/52/AC301581AF00ENG.png)
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(4)
caution |
Do not insert a test probe
into the terminal from its front side directly
as the connector contact pressure may be
weakened.
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Check for continuity between C-119 harness side
connector terminals 36 and 37. OK: Open
circuit
Q.
Is the check result normal?
Erase the
diagnosis code memory, and check the diagnosis code. If
diagnosis code B1400 set, replace the SRS-ECU (Refer to ). Then go
to Step 10 .
Go to Step 9
.
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STEP 9. Check the harness for short circuit between
SRS-ECU connector C-119 (terminal No.36 and 37) and
clock spring connector C-309 (terminal No.3 and
4).
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![](../../../img/52/AC311438AD00ENG.png)
![](../../../img/52/AC313402AD00ENG.png)
![](../../../img/52/AC313412AE00ENG.png)
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Q.
Are harness wires between SRS-ECU connector C-119
(terminal No.36 and 37) and clock spring connector C-309
(terminal No.3 and 4) in good condition?
Go to Step
10 .
Replace the
harness wires between SRS-ECU connector C-119 and clock
spring connector C-309. Then go to Step 10 .
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STEP 10. Check whether the diagnosis code is
reset.
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Q.
Is diagnosis code B1400 set?
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Return to
Step 1 .
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The procedure is
complete.
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