2001 Audi A6 4.2L Quattro

Leave it alone unless you want to continually see the check engine light on

If you have a local mechanic you use, take it into them, have them run a check, maybe $40 to do it, they may find old codes sitting in the system that were cleared but not fully removed. Or if you want to start slow, go to one of the auto shops, autozone or advanced auto, both have scanners you can borrow for free, run it and get the code for the error, then troubleshoot from there.

Anything regarding the check engine light isnt anything too serious.....it could be as simple as a new vas cap but 99% of the time it's yoyr o2 sensor