Temperature

First thing, scan it to get the codes it is storing. That will give you a starting point. However that could be a couple things, one being a stuck open thermostat, that will commonly set a P0128 because the engine doesn't warm up as fast as it should. The other reason could be the cooling fans stuck on, Do you hear a loud rushing sound when the engine is running but setting still? Many parts stores will scan the codes for free. Write down the codes or scan it yourself with a code reader and post them here. You don't need a fancy tool for that, you can get one like the Autel AL329 series at Wal-Mart that works pretty well for powertrain codes.

https://www.2carpros.com/articles/can-scan-controller-area-network-easy