Coolant Temperature Gauge
WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
When engine coolant temperature sensor input indicates temperature exceeds specified range, or gauge moves into the Red area, the engine has become too hot and the PCM will illuminate the CHECK GAUGES light by providing a ground for the light circuit.