Did you pull fuses or relays prior? Sometimes these need removing and reinstalling to reset, same as pulling the battery lead for 10 min and resetting, could also try getting it to learn the update with key and ignition on for a few minutes, followed by off for a few minutes, but possibly not for this.
If it says check power train, then check the power train. You will need a Tech2 plugged in and see what codes have been generated to even begin to know why there is a fault code. It may even be coincidence and unrelated to the serviced part installed.