Indoor Sensor: this code means that the PC board is not receiving a signal from the copper sensing bulb mounted to the side of the evaporator coil.
Diagnosis: visually inspect and/or use an ohmmeter to check the following:
- Sensor has come unplugged from the PC board. OR.
- Sensor has failed and must be replaced. OR.
- Sensor wire has shorted or opended necessitating the repair of the wire.