A.O. Smith 110-310-510 – ERROR CODE 741 [510 (T-D2)], 74 [110 (T-KJR2), 310 (T-K4)] MAIN REMOTE CONTROL PROBLEM

This error code only occurs when there is a miscommunication between the temperature remote controller and the water heater.
1) Check that all wiring is properly connected to the remote.
2) Verify the correct model of remote is being used for the corresponding tankless model.
3) Verify that only a remote is installed. Multiple remotes will result in this error code.
4) If you disconnect the remote from the heater with the power supply on, this error code will result.
Turn off power before disconnecting the remote from the heater.
5) Check for any signs of power surges.