GM Service Manual Online
For 1990-2009 cars only

The speedometer shows the vehicle's speed in both miles per hour (mph) or kilometers per hour (km/h).

The odometer shows how far the vehicle has been driven, in either miles or kilometers.

If a new odometer is installed, the new one is set to the mileage total of the old odometer. If it cannot, it will be set at zero and a label must be put on the driver's door to show the old mileage reading when the new odometer was installed. If the mileage is unknown, the label should then indicate "previous mileage unknown."