Hello Scotty, wasn't sure exactly where to ask this because I'm a little new to your website, but have been a subscriber to your youtube channel for a year. I just replaced my battery on my 2007 Pontiac Grand Prix GT, went to start it up and now my coolant temp gauge on my dashboard does not move. It will do the up then back down when you cycle the ignition, but will not show the reading of the ECT sensor. I hooked up my scan tool and was able to view my coolant temperature no problem. I even checked my fuse for the ECT before using the scan tool to verify it was working. Now to my question, what am I missing that could have happened? I have the code P0116 for the circuit performance, I figured that might give you more information than what I can understand myself.
Could a wire have melted somewhere and I just don't know about it? GM is nasty with their wiring harnesses. I've been working on my car for the last year and never came across something this far over my head. Any help will be greatly appreciated, thank you.

This is where to ask. Odds are the dash unit shorted out, cause your scan tool shows temp sensor is working. Dash units on gms are cheap chinese made junk on those

Thank you so much for the speedy reply, I will be tearing apart my dash and looking for the short to ground tomorrow after work. Luckily the car is not overheating (cause I can see the temp read outs) so the car is drivable, just won't be able to use my remote start in my frosty temps of 10° tomorrow morning due to having the check engine light on :-(