1998 Pontiac Sunfire Temp Gauge

The Temp Gauge in my sons Sunfire only moves when the car is moving…Had a mechanic hook it up too a computer and the temp on the computer went up and down…up and down -14 degrees to 175 degrees…Whats going on ? Temp sensor has bee replaced but did no good…

Is there more than one temp sensor?

The www.autozone.com site states that the coolant temp sensor serves the gage And the CPU (engine computer). The wiring diagram shows that a brown wire and a yellow wire go from the temp sensor to the CPU. Shake the wires under the hood and under the dash and see if the gage readings change. It’s possible the CPU could be at fault.

I’ll Give it a shot …Thanks