Code No.24: Passenger’s
(front) air bag module (squib) system (short-circuited between
terminals of the squib circuit)
OPERATION
- The SRS-ECU judges how severe a collision is by detecting
signals from the
front impact sensors and the front air bag analog G-sensor. If
the impact is over a predetermined
level, the SRS-ECU outputs 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
one passenger’s (front) air bag squib wire shorted
to the other. However, if no diagnosis code resets, the SRS warning lamp
will be switched off
(diagnosis code will be retained).
PROBABLE CAUSES
- Improper engaged connector or defective short
spring*
- Short circuit between the passenger’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).Therefore, if connector
C-132 or C-147 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 diagnosis code
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Q.
Is diagnosis code 34 set?
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 Go to Step
2.
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 Go to Step
3.
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STEP 2. Connector lock check: SRS-ECU connector C-147
(M.U.T.-III diagnosis
code).
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(1)Disconnect the negative battery
terminal.
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(2)Disconnect the connectors C-147
and then reconnect them.
(3)Connect the negative battery
terminal.
(4)Erase the diagnosis code memory, and check
the diagnosis code.
Q.
Is diagnosis code 24 set?
Go to Step
3.
The
procedure is complete. It is assumed that diagnosis code 24
set as connector
C-147 was engaged improperly.
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STEP 3. Connector lock check: SRS-ECU connector C-147
and passenger’s
air bag module connector C-132 (M.U.T.-III diagnosis
code).
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(1)Disconnect the negative battery
terminal.
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(2)Disconnect connectors C-147 and
C-132, and then reconnect them.
(3)Connect the negative
battery terminal.
(4)Erase the diagnosis code memory, and
check the diagnosis code.
Q.
Is diagnosis code 24 set?
Go to Step
4.
The
procedure is complete. It is assumed that diagnosis code 24
set as connector
C-147 or C-132 was engaged improperly.
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STEP 4. Check the diagnosis code by connecting a dummy
resistor (M.U.T.-III
diagnosis code).
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(1)Disconnect the negative battery
terminal.
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(2)Unclip passenger’s air bag
module connector C-132.
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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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Disconnect the passenger’s air bag module
connector C-132 and insert special
tool (MB991866) into the harness side connector by
backprobing.
(5)Connect the negative battery
terminal.
(6)Erase the diagnosis code memory, and check
the diagnosis code.
Q.
Is diagnosis code 24 set?
Go to Step
5.
Replace
the passenger’s air bag module (Refer to  ).
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STEP 5. Resistance measurement at SRS-ECU connector
C-147.
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(1)Disconnect the negative battery
terminal.
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(2)Disconnect SRS-ECU connector
C-147.
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(3)Unclip passenger’s air bag
module connector C-132.
(4)
| danger |
To prevents the air bag from
deploying unintentionally,
disconnect the passenger’s air bag module
connector C-132 to short the squib
circuit.
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Disconnect the passenger’s air bag module
connector C-132.
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(5)
| caution |
Insert an insulator such as a
cable tie to a depth of 4 mm 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 9, 10
and the short spring to release the short spring.
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(6)
| 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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Resistance measurement between C-147 harness side
connector terminals 9 and 10.
OK: Open
circuit
Q.
Is the check result normal?
Go to Step 6
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Repair the
harness wires between SRS-ECU connector C-147 (terminal No.9
and 10)
and passenger’s air bag module connector C-132
(terminal No.1 and 2).
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STEP 6. Check whether the diagnosis code is
reset.
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Q.
Is diagnosis code 24 set?
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Replace the SRS-ECU
(Refer to).
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An intermittent
malfunction is suspected (Refer to GROUP 00, How to Use
Troubleshooting/Inspection Service
Points ).
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