temp gauge not working on 2001 Chevrolet Malibu

where sould i start temp gauge showing nothing as if car was off when the car is on

Asked by for the 2001 Chevrolet Malibu
Check the coolant level, if it is too low, the engine coolant temperature sensor may not be reading the temperature correctly.
If the coolant level is OK, then check the wiring to the temperature sensor. I would also check the diagnostic trouble codes, because this sensor is also used for the emissions system and if there was a problem it would turn on the check engine light and set a trouble code in the engine module.
Other than this, it will require an electrical diagnosis of the temperature gauge, which may need to go to a repair shop.