Front occupant classification sensor rh circuit malfunction

The front occupant classification sensor rh circuit consists of the occupant classification ecu and the front occupant classification sensor rh.

Dtc b1781 is recorded when a malfunction is detected in the front occupant classification sensor rh circuit.

• If troubleshooting (wire harness inspection) is difficult to perform, remove the front passenger seat installation bolts to see the undersurface of the seat cushion.
• In the above case, hold the seat so that it does not tip over. Holding the seat for a long period of time may cause a problem, such as seat rail deformation. Hold the seat up only for as long as necessary.

1. 1
   Check for dtc
2. 2
   Turn the ignition switch on.
3. 3
   Clear the dtcs (see page rs-249).

First clear dtcs stored in the occupant classification ecu and then in the center airbag sensor.

1. 1
   Turn the ignition switch off.
2. 2
   Turn the ignition switch on.
3. 3
   Check the dtcs (see page rs-249).

Dtcs other than dtc b1781 may be output at this time, but they are not related to this check.

1. 1
   Check connection of connector
2. 2
   Turn the ignition switch off.
3. 3
   Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
4. 4
   Check that the connectors are properly connected to the occupant classification ecu and the front occupant classification sensor rh.

3. Check front seat wire rh (to b+)

1. 1
   Disconnect the connectors from the occupant classification ecu and the front occupant classification sensor rh.
2. 2
   Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
3. 3
   Turn the ignition switch on.
4. 4
   Measure the voltage of the wire harness side connector.

Standard voltage

4. Check front seat wire rh (for open)

1. 1
   Turn the ignition switch off.
2. 2
   Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
3. 3
   Using a service wire, connect terminals a4-1 (svc2) and a4-3 (sgd2), and connect terminals a4-2 (sig2) and a4- 3 (sgd2) of connector c.

Do not forcibly insert a service wire into the terminals of the connector when connecting them.

4. Measure the resistance of the wire harness side connector.

Standard resistance

5. Check front seat wire rh (for short)

1. 1
   Disconnect the service wire from connector c.
2. 2
   Measure the resistance of the wire harness side connector.

Standard resistance

6. Check front seat wire rh (to ground)

1. Measure the resistance of the wire harness side connector.

Standard resistance

1. 1
   Check for dtc
2. 2
   Connect the connectors to the occupant classification ecu and the front occupant classification sensor rh.
3. 3
   Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
4. 4
   Turn the ignition switch on.
5. 5
   Clear the dtcs (see page rs-249).

First clear dtcs stored in the occupant classification ecu and then in the center airbag sensor.

1. 1
   Turn the ignition switch off.
2. 2
   Turn the ignition switch on.
3. 3
   Check the dtcs (see page rs-249).

Dtcs other than dtc b1781 may be output at this time, but they are not related to this check.

1. 1
   Replace occupant classification ecu
2. 2
   Turn the ignition switch off.
3. 3
   Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
4. 4
   Replace the occupant classification ecu (see page rs- 392).

Perform the inspection using parts from a normal vehicle if possible.

1. 1
   Perform zero point calibration
2. 2
   Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds
3. 3
   Connect the intelligent tester to the dlc3.
4. 4
   Turn the ignition switch on.
5. 5
   Using the intelligent tester, perform the zero point calibration (see page rs-241).

1. 1
   Perform sensitivity check
2. 2
   Using the intelligent tester, perform the sensitivity check (see page rs-241).

1. 1
   Check for dtc
2. 2
   Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
3. 3
   Turn the ignition switch on.
4. 4
   Clear the dtcs (see page rs-249).

First clear dtcs stored in the occupant classification ecu and then in the center airbag sensor assembly.

1. 1
   Turn the ignition switch off.
2. 2
   Turn the ignition switch on.
3. 3
   Check the dtcs (see page rs-249).

Dtcs other than dtc b1781 may be output at this time, but they are not related to this check.

1. 1
   Replace front seat assembly rh
2. 2
   turn the ignition switch off.
3. 3
   Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
4. 4
   Replace the front seat rh (see page se-8).

   

1. 1
   Perform zero point calibration
2. 2
   Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
3. 3
   Connect the intelligent tester to the dlc3.
4. 4
   Turn the ignition switch on.
5. 5
   Using the intelligent tester, perform the zero point calibration (see page rs-241).

1. 1
   Perform sensitivity check
2. 2
   Using the intelligent tester, perform the sensitivity check (see page rs-241).