Q: Recently my check engine light when on in my 2000 Audi A6 2.7T quattro and I am not too sure of the cause. I recently purchased it about three weeks ago and it has a little under 79k miles on it. The check engine light came on about a week ago and then went off after a couple days. It then went back on yesterday. So, any idea what the issue is? I really am reluctant to get a diagnostics check done, though I will if I have to. Anyway, I hate to say it, but i'm not too good with cars, and I just realized I haven't been putting in premium gas--which the manual says to use. Of course I'm now going to start using preimum gas, but could that be the reason the engine light is on? I can't really test now because the whole tank is full and I have to drive it around some first to get it lower.
A: I wasn't going to answer this, but there are so many other stupid answers.... The check engine light can be cause by MANY different things. There's NO WAY to guess without doing a diagnosis and reading which fault codes are stored. It has NOTHING to do with maintenance. Oxygen sensors are ONE of couple hundred possible reasons. The check engine light's purpose is to tell you that something is wrong that affects emissions control. It may or may not be serious. If it affects emissions control, it may affect the motor and could potentially leave you stranded. Again, without a diagnosis it's impossible to know what it is. If the check engine light comes on initially the best option is to check that the gas cap is tight and drive it for a week to see if the light goes away (unless the motor is not running well). If the light keeps staying on or comes back on you need to get the diagnosis done. I think personally you're better of having that done at an Audi shop where they know the car best, but other shops can do it. A good reason to go to an Audi shop is that you MAY have a problem that is covered by the 8 year/80,000 mile warranty (catalytic converter) since your car is a 2000 and you have less than 80,000 miles on it.