MDAudi

So yesterday morning after a brief drive, my check engine light [more precisely called the "Malfunction Indicator Lamp" (MIL)] lit up on my 2017 A4 and stayed on all day. It stayed on despite turning the car off and on, including after a prolonged (about 3-4 hours) time off. It was on when I parked the car in the garage last night. At no time yesterday did I experience any unusual behavior from the car. Power seemed unaffected.
Now today the check engine light is off.
When it first came on, I made an appointment at my local Audi dealer, but the first available with a loaner was Monday morning. I still have the appointment scheduled, but I am not sure if I should keep it. I am afraid they will find nothing and I will get soaked for the $145 "diagnostic fee".

So, should I keep the appointment, or just wait to see if the check engine light comes on again?

uberwgn

Probably something minor if the MIL went off already. The faults are stored in memory. Go on record and have the dealer record it so you are protected in the future. Simple.

PghRich

Most faults also have a process by which they de-activate the MIL after so many driving cycles without the same fault being detected again. A loose gas cap is always a good example. Tightening the cap won't immediately turn it off, but after 3-5 driving cycles, it will go off. The fault is still stored so you can see what it is, but it's no longer active (and won't prevent any required emissions inspections from being passed).

If it were me, especially with the time and fee involved, I'd cancel and wait to see if it happens again. A $40 OBDII diagnostic tool (or the OBDEleven dongle and app, if you have an Android device) is a great investment.

SchwarzS6

If you are still under warranty there should be no fee and unless you put a lot of miles on your car I would think you would still be covered.

By the way, this is the reason I bought a Ross-Tech VagCOM about 5 Audi’s ago. It has paid for itself many times over.

HyperS4

Had you recently filled up with gas?

Turboale

If you're really curious grab an OBDeleven and then you can keep an eye on it. And unlock some toys here and there...