Yes, I know this is a popular topic, and I've done some reading but I figured I might as well ask in case something else has come up.


Anyways, I have 2004 A4 3.0 with 105K on the ticker.

A few months ago, I had the car in the Audi dealer for an unrelated electrical problem, and they ended up replacing the coil packs under warranty. Recently, the check engine light came on and I had a local shop take a look. They ended up replacing the spark plugs (with the legit OEM ones). Fast forward a couple hundred miles and the check engine light came on. Drove for a few hundred more miles and it went off. It stayed off for probably a week, but I took it back to the Audi dealer to check it out.

I don't know the actual code that was thrown (will try to find out tomorrow), but the Audi dealer said something about the "Bank 1 catalyst". All in, $1700 to replace. Do you think this would warrant a second opinion (like perhaps an O2 sensor or in some way related to the spark plugs), or is this just common enough that I'm going to have to bite the bullet. I have noticed ZERO loss in power or fuel economy by the way.

Again, sorry for beating this topic to death, but thanks for the help.

 

for me it was a bad cat, i had the p0420 code and my check engine light would come on and off from time to time, then it stayed on completely, till eventually i was only boosting 5psi. replaced it with a test pipe since ive got catback and k04 chipped setup, cleared the code and was boosting the normal 16-17 again, your options are a regular cat, hfc (high flow cat), or test pipe (if you dont have emissions in your state). also i wouldnt go to the dealer to do that, if your comfortable working on cars you can do it yourself, its a tight squeeze and patience is needed but its doable with a jack, otherwise find a independent audi/vw mechanic, you will save lots of money