2003 Jetta 2.0 liter, have owned car for 4 months, most of time with CEL light on. (Last month I drove to the Badlands and back no problem.) When the light first came on, maybe in April, I had the codes pulled: P2181 and P0420 (cat. con.).
Last week I failed Illinois' emissions test on account of the P2181 code (though interestingly the test site didn't note the P0420 code). This week I took the car in to a local auto repair shop (not VW specialists) to assist with fixing. They did diagnosis and recommended replacing thermostat (opening too early), which I just had them do today ($314, incl. diagnostic charge). Light is off now, but they wouldn't sign off for me to re-test for emissions because I guess they need a week or so for "readying"? or what I read on here as a "drive cycle"(?).
If the light remains off after seven days (everyone's hope), I take it back to them and hopefully all is good. If the light comes on, our verbal agreement was for me to take the car to the dealer to deal with the P0420 cat. con. code, which they also pulled, which this shop can't deal with. This, of course, is assuming the light comes on because of the P0420 code and not the P2181 code (!).
I hope all goes well, which I guess means that the light won't come on, they complete the paperwork, and I pass the emissions re-test.
I decided to drive to the VW dealer just after this and run by them what this shop did. In a quick chat as the mechanics were picking up their checks, the service manager pointed out a couple things: why didn't this shop also replace the coolant temperature sensor (CTS) since they were in the thermostat area? Why didn't this shop fill out the paperwork and send me right away to re-test since they technically cleared the code for the P2181 fault that the testing site pulled? Both these things sound slightly fishy to him. I'll have to wait a week and see what the story is...
I'll keep you all posted! I guess the worst case scenario is that the light comes back on, and the P2181 code is still there!
P.S. The VW service manager I spoke with about the catalytic converter code says that this code (P0420) is often a symptom of the cooling system issues. VW can replace the cat. con. under warranty (up to 100k, or was it extended?) provided that the catalytic converter code is the ONLY one up.