How do you calibrate a gm electronic speedometer?

To calibrate a GM electronic speedometer, first, connect a scan tool or a calibration tool to the vehicle's diagnostic port. Enter the vehicle's specifications and follow the tool's prompts to set the correct tire size and gear ratiOS. Drive the vehicle at a consistent speed (usually around 30 mph) and adjust the calibration settings until the speedometer reads accurately. Finally, verify the calibration by comparing the speedometer reading with a GPS or another reliable speed measuring device.