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The error code CH02 indicates an "indoor thermistor error" That is a $20 device that senses the air temperature at the face of the indoor coil.
However, it is possible that the thermistor is ok and that the printed circuit board is bad,
Here is a link to the manual for that unit, you can locate the indoor thermistor on the wiring diagram then follow the wires and locate where it plugs into the printed circuit card... remove the two wires and use your ohm meter to see if it is open or shorted.
If you need coaching on that bit of trouble shooting, rate this answer positively and I will throw in the coaching at no charge.