A few weeks ago the check engine light came on in my 2003 Bug convertible (54000 miles). It turned itself off the next day and when I asked a dealer they said it was probably a loose gas cap, despite the fact that the tank hadn’t been filled for a while before the light came on. They wanted to charge me $80 to read the code so I said no thanks. The light came on again yesterday, hasn’t turned itself off yet, and the tank is half full. Is this really the gas cap again, or do I need to pay to have it read?
Have the code read. There is no reason to guess at it. Many auto stores will read the code for free. (The light does not have to still be on to read the code.) Also, a cheap code reader is about $50. Even if you only use it once, that’s still $30 less than your dealer wants.
The gas cap is easy enough to check. It either seals tight or it doesn’t.
Remove and inspect (carefully) the rubber seal on the cap and also the gas filler pipe opening for rust.
Don’t throw the old cap away until you see if the problem IS the cap.
Try the new cap by driving around with the 1/2 tankful. Make certain you turn the cap at least three clicks past tight.
A gas cap won’t cost much and even if it ISN’T a faulty gas cap, you will likely be able to return it back in the package it came in along with the receipt. Just be sure to eliminate the gas odor.
That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.
Your VW has an extended code system and the standard code readers get most of the codes, but will miss some VW specific codes. For those a VAGCOM (Note, there is now a newer version of the reader and they have renamed it, I just can't recall the new name) reader is needed and likely it will not be free.
That said as long as the light is not flashing, I suggest checking out the gas cap and the free reading that the autoparts stores can do before hunting for a VW mechanic with the VW reader.