GM Service Manual Online
For 1990-2009 cars only

The trip odometer tells how far the vehicle has been driven since it was last reset. To set the trip odometer to zero, press the button on the right side of the instrument panel cluster.

The trip/select reset button will go back and forth between the odometer and the trip odometer if the button is pressed and released within 1.5 seconds.

If the button is pressed and held for longer than 1.5 seconds while in the trip odometer mode, it will be reset to zero. If the button is pressed and held for longer than 1.5 seconds while in the odometer mode, it will have no effect.