Hello, I purchased a 2006 TL with 133k miles on it about a month ago. I had it checked out by a local shop prior to purchase, and they said everything looked good. Because of the high mileage they recommended I use seam foam fuel treatment twice a year. Two days ago I filled my tank with 14gal of 93 octane gas from costco, and added a can of sea foam. Today I get a check engine light and a p0420 code. Is it possible that the sea foam caused this? Thanks.

 

Did you put in the whole can?
p0420 is for clogged cats, seafoam in the gas tank won't trigger that

 

Well, Most of the can. I put about 14oz in.

 

Try a few tanks of Shell premium gas and see if it goes away.

 

Does that mean I'd have to keep using shell gas to keep it from coming back? The light went away today oddly enough.

 

There's a chance that seafoam caused it. P0420 can mean any of the following

You should try sticking to Shell, Texaco, Exxon, Mobil, Chevron any of the brand name gas stations that use special fuel additives that helps clean the valves from carbon buildup and other gunk. I've been using Shell V-Power since owning the car in Jan 2011. Never filled up at any other station besides shell. Costco gas may be the least expensive, but keep in mind that you get what you pay for... With a TL as high mileage as yours, I recommend the premium high-grade fuel.

Don't use seafoam again. It's not necessary at all. Just follow the maintenance schedule on time and don't skimp your TL when it comes to gas....

 

Thanks everyone for your input. The code has yet to come back. My gut feeling is that it was the sea foam, but I cant be sure. I'll probably stick to better gas anyway just cause I want to take care of the car.

 

True that, Sea Foam is a joke.

 

Got a link to back up that statement?

Seafoam likely does what it claims, I just don't think it's necessary in our engines nor necessary when running quality deteregent gas in any engine.

 

Exactly, it's a gimmick just like all the other crap that's out there.

 

Still waiting for your link to back up your statement...

 

i think seafoam didnt harm your cats. but you have two cats, front and rear. po420 and po430. its just about that time to replace the warm up cat convertor. seafoam is kind of funky since professionals just stick to using a cansister slow feeding it to the intake vaccum with intake cleaner concerate. my guess is your blaming the wrong thing. time for new cats, dealer price, 800 plus core. gl

 

I too got the P0420 code after using seafoam and up grading my octane 89-93. 2002 jetta VR6. As soon as this tank is empty we will see what happens with a fresh refill. I also notice a burning metal smell from my CAT. I think it's getting pretty toasty in there.

 

The TL is supposed to be run on 91 Octane or above. I think the seafoam triggered the CEL because you knocked off a lot of build up off the engine's exhaust system, fuel injectors, etc and now it's stuck on the metal mesh of the catalyst.

 

If you continue to get the P0420 code try a defouler. I installed one and the CEL has finally disappeared.

 

it wasn't the seafoam it was the previous owner using bad gas. I have put an entire cans of seafoam in my gas (02 CL-S) and never had any issues other than my fuel economy going UP. I have been doing this for 9 years.

I have even put a whole can into my scooter's gas tank and it had no ill effects whatsoever on the machine.