Sensor issues
Up to Audi TT Forum
Last month my TT's rear brake lights stayed on. My neighbor, Boeing analyst, took out the fuses until he found the right one for the lights. I had the switch on the brake pedal replaced but now has a "service engine" light is on. I thought he took out and replaced them one by one but the service mgr told me he might had put them back wrong! $150 per hr to check it out. Does anyone have the right diagram for the fuse box?
Highly unlikely that a swapped fuse would cause a CEL. Probably a loose gas cap. As long as the CEL is not blinking, give it a week and see if it goes away.