P0599 code 2 thermostats later...

So my check engine light came on and I threw I diagnostic tool on it and saw "P0599 - (Thermostat Heater Control Circuit High)". So I purchased a new thermostat (which is part of the housing for 2010 Chevy Aveo) and installed it. Didn't help. My engine was still overheating and having issues. Upon taking it apart again to diagnose it further I accidentally broke the wires on the thermostat plug, so I went ahead and purchased yet another one. Same issue. Three thermostats later (original + 2 new) and same engine code + engine overheating. I heard mentioned somewhere that there might be a thermostat control unit? I also went ahead and replaced the coolant temperature sensor. I know the thermostat is electronically controlled. I checked all my fuses and they are fine. I am wondering if it might be a relay? Visual inspection of the plug itself doesn't show any issues. Anyone have any ideas?