Daikin Heat Pump Error Code CJ

CJ on a Daikin heat pump indicates a remote controller thermistor abnormality. The system has detected that the thermistor inside the remote controller is either disconnected (open circuit) or shorted out while the unit was running. This thermistor measures the ambient room temperature at the controller location, and an invalid reading from it triggers the CJ fault code.

A CJ fault means the system has lost a valid temperature reading from the remote controller thermistor, which can affect how accurately the unit responds to setpoint commands. While the heat pump may continue to operate, its temperature control accuracy could be compromised. It is advisable to clear the code and monitor the unit, and to resolve the fault promptly if the code returns.

Resetting the code clears the stored fault record, but if the underlying thermistor fault is still present, CJ will reappear once the unit runs again. A successful reset that does not return suggests the fault was intermittent. A persistent CJ after multiple resets is a reliable indicator that the remote controller needs to be replaced.

You can attempt the reset procedure yourself: enter inspection mode on the remote controller, display the CJ code, then press and hold the ON/OFF button for 4 seconds or more to clear the stored fault. If the code does not return, the fault may have been intermittent. If CJ reappears after the reset, the remote controller will need to be replaced, which is a straightforward task but does require sourcing the correct replacement part for your model.

If the fault is resolved by clearing the stored code with no hardware replacement, there is no parts cost. If the remote controller needs to be replaced, parts costs typically range from around $80 to $250 or more depending on the specific Daikin model and controller type. If a technician is needed for diagnosis or installation, labor costs will add to that range.