Problem: Temperature guage does not return to zero when ignition is turned off.

Vehicle: 2004 buick lesabre custom

3800 v6

vin: 1G4HP52K34U223203

mileage: 78,959

area of operation: Chicago, illinois area

problem: Temperature guage does not return to zero when ignition is turned off.

i noticed that temperature guage would go into the red after a driving sequence, so i thought car was overheating. (never had an overheating problem with this vehicle in the past)

the scanner showed no codes. No coolant leaks, coolant reservoir is full.

Scanner show operating temperature at 195 f.

Solutions tried: I then replaced the thermostat, temperature sensor, and radiator cap, and water pump, belt tensioner, then bleed the system. I am sure the car is not overheating. (note: If i switch the ac on both radiator fans run. If i remove the wire from the temperature sensor, both radiator fans run.) battery was replaced in 2018. Car starts and runs fine with no issues.

After a couple of driving sequences, the guage will red line and not return to zero when the car is turned off cooled off. In order to get the temperature guage back to zero, car needs to cool off. Then, i need to cycle the key, with out starting, several times, maybe (10), to lower the guage needle back down to zero, or remove the fuse for the computer, and do the same. Note: All other guages work properly, and all indicator lights will turn on.

Question: Does this sound like a bad stepper motor for the temperature gauge, or a computer problem, or a programing problem? I have no experience with stepper motors, or if this is even the problem. In 53 years of driving, i have never had a guage , or computer malfunction. Does any one have any ideas?