GM Service Manual Online
For 1990-2009 cars only

The tachometer shows engine speed in thousands of revolutions per minute (rpm). You can use it while driving to select correct shift points. The tachometer may not return to zero when the engine is not running.

Notice: If the engine is operated while the tachometer is in the shaded warning area, the vehicle could be damaged, and the damages would not be covered by the vehicle warranty. Do not operate the engine with the tachometer in the shaded warning area.