Code No.B1401: Driver’s Air Bag Module (1st Squib) System
Fault 2 (Open in the Squib Circuit)
![](../../../img/52/W4X52X001A00ENG.png)
caution |
If diagnosis code B1401 is set in the
SRS-ECU, always diagnose the CAN main bus line.
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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:
- Open circuit in the driver’s air bag module
(squib) or harness
- Open circuit in the clock spring
- Malfunction of connector contact
PROBABLE CAUSES
- Open circuit in the clock spring
- Open circuit due to improper neutral position of the clock
spring
- Open circuit in the driver’s air bag module (squib)
circuit
- Disengaged driver’s air bag module (squib)
connector
- Improper connector contact
- Malfunction of the SRS-ECU
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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. 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
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 4
.
Replace the
driver’s air bag module (Refer to ). Then go
to Step 6 .
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STEP 4. 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 harness side of
clock spring connector C-309 (terminal No.4 and 3) 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 5
.
Replace the
clock spring (Refer to ). Then go
to Step 6 .
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STEP 5. Check the harness between the SRS-ECU connector
C-119 (terminal No.36 and 37) and the clock spring
connector C-309 (terminal No.3 and 4) for open
circuit.
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![](../../../img/52/AC311438AD00ENG.png)
![](../../../img/52/AC313402AD00ENG.png)
![](../../../img/52/AC313412AE00ENG.png)
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(1)Disconnect SRS-ECU connector
C-119 and clock spring connector C-309.
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![](../../../img/52/AC313270AC00ENG.png)
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(2)
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 the following
terminals.
- SRS-ECU connector C-119 (terminal No.36) and the
clock spring connector C-309 (terminal
No.3)
- SRS-ECU connector C-119 (terminal No.37) and the
clock spring connector C-309 (terminal
No.4)
OK: Less than 2 Ω
Q.
Are the check results normal?
Erase the
diagnosis code memory, and check the diagnosis code. If
diagnosis code B1401 set, replace the SRS-ECU (Refer to ). Then go
to Step 6 .
Replace the
harness wires between SRS-ECU connector C-119 and clock
spring connector C-309. Then go to Step 6 .
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STEP 6. Check whether the diagnosis code is
reset.
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Q.
Is diagnosis code B1401 set?
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Return to
Step 1 .
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The procedure is
complete.
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