You are setting a coolant temp dtc. The fans will go full on, hvac off, and some of your gages will go full on (max) or off (min) so you will notice the fault in case the vehicle is actually over-heating. The reason it returns to normal with a reflash or battery dis-connect is b/c you are clearing the dtc. You need to make sure the dtc's are turned on in your tune for now so you can pinpoint the issue by following the dtc diagnostics. Once you pull you dtc's, you can report back or look up the diagnostic chart for the specific dtc(s). Since you have a tech 2 you can easily pull dtc's. You can turn off your dtc"s , but that's not going to fix you actual issue.