- Check if each sensor is mounted.
- If an error occurs when checking the CS31A (3 CST FM B/D CN3) disconnection operation, replace a sensor.
- If an error occurs when checking the CS31B(3 CST FM B/D CN3) disconnection operation, replace a sensor.
- Check if the CDU Board CN6 and 3 Cassette FM Board CN1 are connected.
- Check settings of 3 Cassette FM Board Dip Switch (#2, #4, #6 On)