GM Service Manual Online
For 1990-2009 cars only

The speedometer shows the vehicle's speed in both miles per hour (mph) and kilometers per hour (km/h). The odometer shows how far the vehicle has been driven in either miles (used in the United States) or in kilometers (used in Canada).

This vehicle has a tamper-resistant odometer. If the odometer displays ERROR, it probably has been tampered with and the numbers might not be accurate.

If the vehicle needs a new odometer installed, it must be set to the mileage total of the old odometer. If that is not possible, then it will be set at zero and a label must be put on the driver's door to show the old mileage reading of the vehicle when the new odometer was installed.