Code No.B1B13 Driver’s knee air bag module (squib) system (short circuit between squib circuit terminals)
| caution |
If the diagnosis code B1B13 is set to SRS-ECU, be sure to diagnose the CAN bus line.
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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 knee air bag module (squib).
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The code is set when the short circuit occurs to between the terminals of SRS-ECU knee air bag module (squib) circuit.
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- Damaged short spring *
- Short circuit between terminals of knee air bag module (squib) circuit
- Damaged connector(s)
- Malfunction of SRS-ECU
- Insufficient press of locking button or locking button not pressed
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| note |
*: The squib circuit connectors integrate a short spring (which prevents the air bags from being unintentionally deployed because of static electricity by shorting the positive wire to the earth wire in the squib circuit when the connectors are disconnected). Therefore, when the above codes are set, the short spring may not be released due to the damaged connector even when the connectors are connected.
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STEP 1. M.U.T.-III CAN bus diagnostics.
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Use 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 54C - Troubleshooting  ).
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STEP 2. Check whether the diagnosis code is reset.
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(1)Connect the negative battery terminal.
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(2)After erasing the diagnosis code memory, check the diagnosis code again.
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(3)Disconnect the negative battery terminal.
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Q.
Is the diagnosis code No. B1B13 set?
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Go to Step 3.
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
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STEP 3. Connector check: C-122 SRS-ECU, C-25 knee air bag module.
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(1)Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
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(2)While pushing the part "A" indicated in the figure of the harness side connector, turn the lock lever to the direction of the arrow to release the lock lever. After disconnecting the C-122 SRS-ECU connector, connect it again.
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(3) After disconnecting the C-25 harness side connector, connect the connector again. For the C-25 harness side connector disconnection, use the flat-tipped screwdriver to pull out the harness side connector locking button. After releasing the lock, disconnect the harness side connector.
(4)Connect the negative battery terminal.
(5)After erasing the diagnosis code memory, check the diagnosis code again.
(6)Disconnect the negative battery terminal.
Q.
Is the diagnosis code No. B1B13 set?
Go to Step 4.
Repair the connector.
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STEP 4. Diagnosis check by dummy resistor connection.
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(1)Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
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(2)Use the flat-tipped screwdriver to pull out the locking button of harness side connector. After releasing the lock, disconnect the C-25 harness side connector.
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(3)Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991884).
(4)Connect the resistor harness to the C-25 harness side connector.
(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. B1B13 set?
Go to Step 5.
Replace the driver’s knee air bag module (Refer to ).
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STEP 5. Resistance check at the C-122 SRS-ECU connector.
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(1)Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
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(2)While pushing the part "A" indicated in the figure of the harness side connector, turn the lock lever to the direction of the arrow to release the lock lever, and disconnect the C-122 SRS-ECU connector.
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(3)
| danger |
To release the SRS-ECU connector short spring in the following operations, disconnect this harness side connector, and keep the squib circuit shorted.
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Use the flat-tipped screwdriver to pull out the locking button of harness side connector. After releasing the lock, disconnect the C-25 harness side connector.
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(4)
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The short spring may not be released due to the insufficient insertion. Therefore, insert the insulator for 4 mm or more.
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Insert an insulator (width: 3 mm, thickness: 0.5 mm) such as cable tie between the terminal No. 1 and 2, and then release the short spring.
(5)Take the measurements below at the C-122 harness side connector.
- Continuity between terminals 1 and 2
OK: No continuity
Q.
Is the check result normal?
Go to Step 6.
Repair the wiring harness between the C-122 SRS-ECU connector terminal No. 1/2 and the C-25 knee air bag module connector terminal No. 2/1.
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STEP 6. Check whether the diagnosis code is reset.
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Q.
Is the diagnosis code No. B1B13 set?
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Replace SRS-ECU (Refer to ).
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
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