GM Service Manual Online
For 1990-2009 cars only

The speedometer displays the speed in either miles per hour (mph) or kilometers per hour (km/h).

There is only one scale for mph and km/h. Use the Driver Information Center (DIC) controls to switch between mph and km/h. See DIC Operation and Displays for more information. The cluster will calculate the proper speed and move the needle to the correct position. Either the MPH or the km/h telltale will illuminate, depending on which measurement is chosen.

The odometer is part of the Driver Information Center (DIC). See DIC Operation and Displays for more information.