I literally get the gas cap CEL every other week. It eventually resets itself after 4-6 cycles but it is still annoying. Do I need to get a new gas cap? Would that help? Would it help to connect vagcom and do some kind of clear that would make it go away for good, as long as I make sure the cap is tight? I have never not tightened the cap...which is why it's annoying me.

 

How do yo know the Cel is related to the gas cap if you don't read it? And if cap related, maybe you need a new one.

 

VCDS.... There is no such thing as a "gas cap CEL" AFAIK. There is a small vapor leak code in OBDII and a large vapor leak code. Small is the more likely gas cap, but it can be like 10 other things too--hoses, bad filler, bad vapor check solenoids, cracked or faulty carbon canister, etc. Hence VCDS instead of a crude code reader to get more info. Fortunately Audi isn't known for a lot of issues in the vapor system unlike some others. On an older E class, you would be the luckiest owner in the world if it were "only" the gas cap.

At least go to some auto parts place for the crude read to get beyond "gas cap CEL." Another example where VCDS can pay for itself quickly.

Also, depending on state you are in, miles and year, may be covered technically under emissions warranty. Open the glove box for that and start reading. But as always, if minor not worth the overhead usually to try to get dealer/Audi to admit coverage. If 4/50, no brainer to take it in. You should include year, motor and general location in sig. or avatar for these sorts of reasons--better answers result.

 

I even got a pair of cats for my 02S6 within the extended emissions warranty. Normally emissions equipment are warranted for 8yrs/80K miles
unless you've boogered it somehow, like with an aftermarket tune that burns out the cats

 

What code number do you receive? There is a known problem with gas gauges and gas tanks on D4. If I fill up when the gauge reads more than half full I get a check engine light nearly every time. Dealer has said it has been a problem across the Audi model line and there is a software correction but it hasn't yet been sent out for the S8.

As long as I wait until the gauge reads less than half full when I fill up I don't have any problems.

 

I have VCDS, so I will plug it in and check it out. Always just assumed it was the cap as it would happen after fueling up and would clear itself after a few cycles. I have a 2015 Audi S8 that has had the vibration TSB correction. It has 16k miles, so it is well within warranty.

BTW, I am looking at my avatar/sig and it shows I am in Iowa; states I have a 2015 S8, which should also indicate the motor. Is this not showing up for others to see?

 

Mine is in for 15K service right now and I am having them look at a gas gauge issue. I don't get any CEL's but it would read only about 5/8 full after fill ups last fall. REDHORSE is reporting the same below, though also a CEL in his case. Mine would creep back to full by about 30 miles later. It went away last winter and I haven't seen it since.

Some one on AZ board for C7's reported there was apparently ECU flash for what sounds like the gauge issue on 2015 RS7's (also pre Plus/Competition). Came up because he was trying to get an APR tune and APR had no file for the revised Audi flash. Apparently since updated by APR for those with it (not me), but meantime I will report anything I find out w/ dealer. Service advisor was unaware of any update of issue here--though said there were lots of issues with new design A3 fuel readings they were dealing with. But at end of week they apparently ordered something--sounded like software they needed in a physical format--so I will see.

P.S. Weird on avatar/sig. Your original post below doesn't have the car ownership in the signature (at least on my screen), but the reply does. In past, when I change my sig. it shows up as revised in any of my old posts too when I search for something. But I have noticed off and on flakiness with signatures for 6 months. More so with pics for mine before I deleted.

 

Update: plugged in the Vag and got a code for lean reading on secondary O2 sensor. Saved readout and cleared. Will see when it reappears.