It sounds like a switch setting got changed. The engineers at GM think you do not know how to turn lights on yourself, so they like to add a lot of automatic stuff, including headlights. Dimming dash lights sounds like what is supposed to happen when you turn on the head lights.
About once a week I see someone zipping merrily through town at night with no tail lights or running lights, and it is always a GM vehicle. Only the headlights are on, but less than full brightness. The drivers are not even aware they cannot be seen.
Part of the alignment procedure involves using a bar to hold the brake pedal depressed. Some mechanics will remove a fuse or do something else to keep the brake lights off so the battery does not run dead. Perhaps he forgot to undo whatever he did. There are also some "customer preference" settings that may be involved with this issue. Most of the time you need a scanner to access the Body Computer to change those, but there are some that can be changed by the driver by pressing specific sequences of switches. One of those setting may have changed.
Regardless of what happened, the place to start is by returning to the same shop right away. I know it is hard to believe, but just like with doctors, we do make a mistake every once in awhile, and we deserve the chance to correct them.
Monday, December 5th, 2016 AT 8:02 PM