Warning light came on it warned I had 1000 miles to go. Added 2.5 gallons, all was good and warning went bye bye. 150 miles later warning was back and the miles are declining from the initial warning. Added another 2.5 gallons and warning is still there and it's down to 450 miles.of range. I think it said I can't re-start it at that point. Or does it go into limp mode? Any help would be appreciated.

 

If you were able to add 5 gallons of DEF, then it was pretty low. IIRC, the whole system only holds about 7 gallons +/-, and most of that is in a holding tank under car. The 'operating tank' is right there adjacent to the fill cap, and that's the one that is being monitored..only holds about 2.5 gallons. It is 'normal' for it to take a little time (or special key sequences) to get the DEF monitoring system to 'check' itself and reset the warning. You can search google to locate the key sequence; I've seen it but never needed it, so...out of sight, out of mind.

In rarer cases, like on my car, you can have a sensor fault that creates a feedback loop error, and that creates a 'bouncing' effect with the miles to shutdown displayed, where it randomly counts down and then go up/down/up, etc. on how many miles remain till it reaches no-restart stage. That was occurring even after dealer filled the tanks fully, and so they tracked it to being a bad sensor. The next time it counted down on me was due to the transfer pump from the lower/main storage tank had gone out, so the 'working tank' wasn't getting replenished, thus the countdown. Mine was all fixed under TDI warranty, which includes free DEF refills.

Rule of thumb is the DEF fill should last approx 1 oil change interval, that is unless you are towing or doing other driving that tends to consume more DEF. With the emissions 'fix' implemented, many TDI owners report it doesn't last a full oil change interval for them, as the 'fix' turned up the DEF system's activity & volume to reduce emissions further.

 

Drove 15 miles and it reset itself. Kind of a PITA when your out of town and home is beyond the 400 miles.

 

Yeah, but once you understand how the system 'works', and that there is an inherent delay before it resets itself, you know what to expect and don't stress on it. Also, you begin to plan better and include the DEF tank fill-up as part of your travel/road-ready checklist, if it hasn't recently been done, etc. You can also look up your level of DEF in VCDS. Don't overtorque that fill cap though, as they can crack, and are silly expensive to replace that bit of plastic.

BTW, DEF has approx a 1yr shelf-life in a sealed container (a surprising fun fact) so don't go buy a ton of it to keep on-hand, and be sure to check the use-by/freshness dates on it.

 

I don't own a diesel but I thought I'd read somewhere that Audi is supposed to provide DEF for all cars if they're still under warranty. I could be wrong so don't quote that as fact.

 

Yes, if still covered by the extended TDI warranty, then all you need do is request it from the dealer. I always have them fill our DEF when I take one in for warranty work. They tried to charge me for it once, and I told them they'd better go read the warranty document I had provided them. The surprisingly high charge for a DEF top-off was removed.

It's not worth my driving to a dealer just to get DEF, but it's a good perk while it lasts (warranty remaining on both cars), so long as you remember to ask for it.

 

And when that warranty is over all that crap is coming off.

 

 

I had the same problem with the light coming on and they had to change my transfer pump with 28K. And yes DEF is fill up for free at the Stealer until 100 K if I'm not mistake. If the light does comes on, stop by and they are suppose to fill it up for FREE.

 

I use VCDS to reset the Level Sensor after DEF fillup's. Sometimes it'll reset itself instantly, sometimes it takes quite a long drive. Engine on/ off, slanted driveway/ flat ground... Same result, I've noticed.