Open VCM Scanner on your computer. Connect your tuning interface to the computer and the vehicle's OBD2 port.

Turn the ignition to the ON/RUN position (but do NOT start the vehicle)

Once the VCM Scanner has connected to the vehicle, click the "Vehicle Controls and Special Functions" button.

Turn the key to the OFF position. Your transmission's learned shift adaptives have now been reset. The transmission will now learn the new desired shift behaviors over the course of the next \~100 miles.

The first few shifts during the relearn period may be VERY weird. This is normal. This is the result of the transmission getting a feel for the new settings. This will settle down with continued driving. During these weird shifts, just drive like they're not even happening. Keep the throttle input consistent (i.e. don't snap the throttle shut if the shift is weird), and just keep on driving.

Hptuners

This guide walks you through resetting the stored transmission shift characteristics using HP Tuners VCM Scanner. Resetting these parameters will force the transmission to relearn the new desired shift properties.

Reset GM Transmission Adaptive Settings