Code No.B1431: Side-airbag module (LH) (squib) system (open-circuited in the squib circuit)
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If diagnosis code B1431 is set in the combination meter, 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 (squib) (LH) 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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| warning |
Since the radiator fan rotates during CAN bus line diagnostics, make sure that no one is servicing the engine compartment before diagnosing the CAN bus line. Since the CAN communication stops when diagnosing the CAN bus line, the ETACS-ECU detects the time-out of the engine-ECU, and activates the radiator fan to prevent overheating as fail-safe.
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Use the M.U.T.-III to check the CAN bus lines.
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Q.
Is the CAN bus line found to be normal?
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 Go to Step 2.
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 Repair the CAN bus lines (Refer to GROUP 54C, Troubleshooting - Can Bus Diagnosis Table  ).
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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)Turn the ignition switch to "ON" position.
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(3)Check if the diagnosis code is set.
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(4)Turn the ignition switch to the "LOCK" (OFF) position.
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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) (M.U.T.-III diagnosis code).
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(1)Disconnect the negative battery terminal.
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(2)Disconnect the side-airbag module (LH) connector C-20.
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(3)Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).
(4)
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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 resistor harness (MB991866) into the C-20 harness side connector by backprobing.
(5)Connect the negative battery terminal.
(6)Erase diagnosis code memory, and then check the diagnosis code.
Q.
Is diagnosis code B1431 set?
Go to Step 4.
Replace the side-airbag module (LH) (Refer to ).
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STEP 4. Resistance measurement between the SRS-ECU connector B-109 (terminal No.15 and 16) and the side-airbag module (LH) connector C-20 (terminal No.1 and 2).
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(1)Disconnect SRS-ECU connector B-109.
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(2)Disconnect side-airbag module (LH) connector C-20.
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(3)
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Do not insert a test probe into the C-20 connector terminal from its front side directly as the connector contact pressure may be weakened.
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Resistance measurement between the following terminals.
- SRS-ECU connector B-109 (terminal No.16) and the side-airbag module (LH) connector C-20 (terminal No.1)
- SRS-ECU connector B-109 (terminal No.15) and the side-airbag module (LH) connector C-20 (terminal No.2)
Q.
Are the check result normal?
Go to Step 5.
Repair the harness wires between SRS-ECU connector B-109 (terminal No.15 and 16) and side-airbag module (LH) connector C-20 (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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