Car won't start. Temp shows vehicle is overheating but it is not.

Check the under-hood fuses as well. The car has a failsafe to shut off if temp hits redline while out of gear or at idle. Connect a scanner, clear the codes, change any bad fuses under the hood, fill with coolant with the ignition ON engine OFF and then try to start. If it is a no-go, test the sending unit. It may still be registering that you are overheated. Does the engine crank and not start, or does it do nothing?