Code No.B1431: Side-airbag squib (LH) open-circuited
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caution |
If diagnosis code B1431 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 left and right side impact sensors. If the impact is over a
predetermined level, the SRS-ECU sends an ignition signal. At this time, if
the side-airbag safing G-sensor is on, the SRS side-airbag will
inflate.
- The ignition signal is input to the side-airbag module to inflate the
side-airbag.
DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set if there
is abnormal resistance between the input terminals of the side-airbag module
(LH) (squib).
PROBABLE CAUSES
- Open circuit in the side-airbag module (LH) (squib) circuit
- 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 lines (Refer to GROUP 54D, Diagnosis-Can Bus Diagnostic Chart
).
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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 side-airbag module (LH).
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(1)Disconnect the negative battery terminal.
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(2)Disconnect the side-airbag module (LH) connector
E-121.
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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 the E-121 harness side connector
by backprobing. (5)Connect the negative battery terminal. (6)Erase
the diagnosis code from memory, and then check the diagnosis code.
Q.
Is diagnosis code B1431 set?
Go to Step 4.
Replace the seatback frame of the
front seat (LH) (Refer to GROUP 52A, Front Seat ).
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STEP 4. Resistance measurement between the SRS-ECU connector D-25
(terminal No.9 and 10) and the side-airbag module (LH) connector E-121
(terminal No.1 and 2).
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(1)Disconnect the negative battery terminal.
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(2)Disconnect SRS-ECU connector D-25 and the side-airbag
module (LH) connector E-121.
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(3)
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 D-25 (terminal No.9) and the side-airbag module (LH)
connector E-121 (terminal No.1)
- SRS-ECU connector D-25 (terminal No.10) and the side-airbag module (LH)
connector E-121 (terminal No.2)
OK: Continuity (Less than 2 Ω)
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Q.
Are the check results normal?
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Go to Step 5.
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Repair
the harness wires between SRS-ECU connector D-25 (terminal No.9 and 10) and
side-airbag module (LH) connector E-121 (terminal No.1 and 2).
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STEP 5.Check whether the diagnosis code is reset.
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Q.
Is diagnosis code B1431 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 Cope with
Intermittent Malfunction ).
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