Code No. B1401: Driver’s
air bag module (squib) system (open circuit of squib
circuit)
caution |
If the diagnosis code No.
B1401 is set to SRS-ECU, be sure to diagnose the CAN bus
line.
|
|
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).
|
|
The code is set when the open
circuit occurs to the SRS-ECU driver’s air bag
module (squib) circuit.
|
|
- Open circuit in the clock spring
- Open circuit due to improper neutral position of the
clock spring
- Open circuit to driver’s air bag module
(squib) circuit
- Disengaged driver’s air bag module (squib)
connector
- Poor contact of connector
- Malfunction of SRS-ECU
|
|
STEP 1. M.U.T.-III CAN bus diagnostics.
|
|
Use M.U.T.-III to diagnose the CAN
bus lines.
|
|
Q.
Is the check result normal?
|
|
Go to Step
2.
|
|
|
|
Repair the CAN bus
line (Refer to GROUP 54C - Troubleshooting ).
|
|
|
|
STEP 2. Check whether the diagnosis code is
reset.
|
|
(1)Connect the negative battery terminal.
|
|
(2)After erasing the diagnosis code memory, check
the diagnosis code again.
|
|
(3)Disconnect the negative battery
terminal.
|
|
Q.
Is the diagnosis code No. B1401 set?
|
|
Go to Step
3.
|
|
|
|
Intermittent
malfunction.
|
|
|
|
STEP 3. Diagnosis check by dummy resistor
connection.
|
|
(1)Check that the negative battery terminal is
disconnected. If the negative battery
terminal is connected, disconnect it.
|
![](../../../img/52/ACB04316AB00ENG.png)
|
(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).
|
![](../../../img/52/AC905251AC00ENG.png)
|
(4)
caution |
Do not insert a probe directly
into the terminal from the connector
front side as the connector contact pressure may
be weakened.
|
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 the diagnosis code No. B1401 set?
Go to Step
4.
Replace
the driver’s air bag module.
|
|
STEP 4. Diagnosis check by dummy resistor
connection.
|
|
(1)Check that the negative battery terminal is
disconnected. If the negative battery
terminal is connected, disconnect it.
|
|
(2)Disconnect the clock spring connector.
|
![](../../../img/52/AC905254AC00ENG.png)
|
(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.
|
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 the diagnosis code No. B1401 set?
Go to Step
5.
Replace
the clock spring.
|
|
STEP 5. Resistance measurement at the SRS-ECU and the
C-313 clock
spring connectors.
|
|
(1)Check that the negative battery terminal is
disconnected. If the negative battery
terminal is connected, disconnect it.
|
|
(2)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.
|
Disconnect the clock spring connector.
|
![](../../../img/52/ACF04632AD00ENG.png)
|
(4)
caution |
The short spring may not be
released due to the insufficient insertion.
Therefore, insert
the insulator for 4 mm or more.
|
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)
caution |
Do not insert a probe directly
into the terminal of clock spring connector
harness side connector from the connector front
side as the connector contact pressure may be
weakened.
|
Take the measurements below at the SRS-ECU connector
and clock spring connector harness
side connectors.
- Continuity DQ1- line between SRS-ECU connector and
clock
spring connector
- Continuity DQ1+ line between SRS-ECU connector
and clock spring connector
OK: Continuity (less than 2
Ω)
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.
|
|
STEP 6. Check whether the diagnosis code is
reset.
|
|
Q.
Is the diagnosis code No. B1401 set?
|
|
Replace
SRS-ECU.
|
|
|
|
Intermittent
malfunction.
|
|
|