Picked up my new 07 a week ago from a dealer in the Chicago area and lovin' it. Milltech exhaust. When I first left for the 500 mile run home, the check engine light came on. Went back to the dealer. Ran a Working Log which said the cat system efficiency was below threshold for both banks. The dealer said this had not been an issue before, and thought it was a result of starting/stopping/idling and not being driven for a while. Went out for a blast to wring it out. Light eventually came back on, but this time the Log said only one bank had a problem which seemed to support the dealer's theory. I had to hit the road, so I left. WONDERFUL ride home. No problems and no light. Having a tough time not driving it, and have put on a bunch of satisfying miles. However, today the light just popped back on again. This time it can't be from lack of driving. If the dealer keeps to his word, he'd send me a factory exhaust system, but I really like the sound of this Milltech. Any input would be appreciated.

 

Same thing happened to me, different brand of exhaust.
Running around town would cause CEL to come on, a few high speed runs would turn it off.
If you like the exhaust and don't want to change to a different brand that does not cause the CEL to turn on, an ecu tune will fix it.

I have a softronic tune that fixed my CEL issue, has not come on since I flashed my ecu.

 

Thank you for taking the time to respond. At least this gives me some direction, and hopes I might still be able to keep this exhaust. New territory for me and the learning curve seems a bit steep right now. In the meantime.......some pix (but don't know why they only show as thumbnails).......

 

This is not an uncommon problem with after market exhausts. I had the same problem with my Fabspeed, but they replaced the cats and I have not had a CEL since.

 

Boy I love a black car when its clean and shiny!!

 

Just a few things...

What type of cats are attached to your exhaust system? 100 cell or 200 cell? Milltek (not Milltech) manufacturers both. 100 cell cats require ECU reprogramming to prevent CELs. 200 cell cats (if functioning properly) should not require ECU reprogramming. If it is the later, and this is a new problem, then either your O2 sensors are bad or your cat setup is the problem...you can call Milltek to see if you qualify for an cat swap...they offer a limited lifetime warranty if you are the original purchaser.

Some tuners will offer you a flash that will correct the CEL. It is my opinion that a properly working cat setup that uses 200 cell cats shouldn't require an ECU sensor shutoff. If your exhaust uses 100 cell cats, the CELs have probably been an issue since the exhaust was installed, and will require an ECU flash to resolve the issue.

 

you can try using a o2 sensor bung

 

Thanks for the response (and sorry for the Milltek misspelling). I know they make 100s and 200s, but don't know which I have. Did find serial # plates so I hope to find out using those. I am not the original purchaser so I wouldn't qualify for a swap. He traded it to the dealer I bought it from. Other than the exhaust, there are no other mods. The cats appear to be a welded, integral part of the exhausts on each side, not separate. I've only owned the car a week. 13K miles and CPOd.
Do you know if the Working Log would have indicated bad O2 sensors? Might it be possible to call up how many times the CEL has come on? I would tend to agree this is not a new issue, but the dealer said they were not aware of it and this guy was their customer. At any rate, you have given me even more things to explore for which I am grateful.

 

Jonnydeep83, I tried to respond to your PM but the site won't let me until I have a minimum number of posts. Sorry.

 

Searched this. Seems to have worked for you. Think I need to get my arms around what I'd actually be doing by using those before I jump in. Thanx

 

I'm pretty certain it's a cat inefficiency code with that brand of exhaust. Seen that multiple times. Get an OBDII scanner and see what the code is. Milltek has had known issues with their HJS cats in the past;(