Thread: p0420

Originally Posted by smoke14

Just do what Billboost said, hes always right. Or buy a quality Walker cat. High flow cats arnt worth it.

Walker doesnt make one for the gxp yet according to the shop i go to. only one available is through GM

This applies to several threads, if people want to just throw money and not take our advise send me the money so I can go buy a case of new bowties if ya know what i mean.

Not to be harsh, but it is still freaking snowing wet heavy slushy crap south of the Twin Cites and it is April 18.

I already have this ScanTool 425801 OBDLink SX OBD-II Scan Tool USB Interface with OBDwiz Diagnostic Software : Amazon.com : Automotive

I use it to check/turn off my codes. Ive had it awhile. Is there any way I can use the cable to tune or do i need the 'box' that comes with most tuning packages??

From what I'm reading, it's probably a good idea to tune the car so no matter what i dont get the p0420, that way i can save fuel.

Edit:

I looked at a different topic that has the same issue and apparently the non-fouler just screws into the exisiting o2 sensor hole then you install the o2 sensor? Im guessing that'll give the o2 sensor less room inside of the exhaust pipe so it reads less emissions? Kind of faking it out. Sounds like it may work. I see online an 18mm one, is that what i need?? thanks everyone!!

Buy Dorman - Help Spark Plug Non-Foulers - 18mm Gasket Seat 42009 at Advance Auto Parts


thats the ones i found. will that fit? the other thread was confusing, how does it need to be done exactly? I can install it when i replace the o2 sensor

Dont replace the o2. Jesus man everyone is telling you to do the defouler trick. It moves the 02 sensor out of the exhaust a bit and tricks it. costs less then 5$ and it always works. I have a 3 inch straight pipe with NO CAT WHATSOEVER and no rear o2 codes at all. I havent even bothered to tune out the o2 checks with my hptuners. It just works.

Aftermarket cats NEVER make the computer happy so dont replace the o2 or anything else just use the defouler trick. Screw your old o2 into a defouler, Might have to drill the defouler out with 1/2 inch drill bit. Then screw it into the exhaust. Done.

I already had the o2 sensor. Might as well replace it while im under there anyways, the old o2 sensor had substrate from the blown cat we replaced.
SO i only need to use one defouler? I think it comes 2 in the pack.
18mm diameter it says

You could spend that 100+ dollars on a nice cold air intake or something. Or take your lady friend out on a nice date.... but anyways you can use as many as you want. I had to use 2 to make it happy. If your willing to spend the money on a 02 why not just get a 02 Simulator from zzp? Cheaper then an o2 and youll never have a code again. Easy Performance - O2 Emulator #EP-O2SM-GM01

The simulators don't work on 04+ the fouler won't work either based on my experience with it plus the e67 pcm looks for different readings on the rear 02. You could try the fouler if you want hell it might work but its not guaranteed like a tune.

Originally Posted by sirricealot

The o2 is too tight so I cant get it off using a floor jack. Gotta have a shop do it. And I didn't have a vice to hold the defouler so I couldn't get it drilled yet. Clesred all codes for now

Use a 7/8 wrench hit the the end of wrench with hammer the correct direction

Iv never had a non fouler not work. Took 3 non foulers on my buddies 04 but it worked without a cat at all.

I was doing this with a jack and stands. I tried and tried to get it off but they obviously put it back on with an impact . Crossing my fingers but so far the code hasn't came back since I cleared ALL of them. It seemed like I had to clear them like 4 times to get them to clear completely, maybe when the shop 'cleared' the code they only cleared the most recent one.

FWIW, I made the suggestion based on others experience. Because I didn't know what it was etc, I googled it and watched a youtube on it. Looks like most use 2 defoulers and conveniently they come as a two pack.

Hopefully the light doesnt come back on. If it does I'l have to drill out the defoulers and see if someone can loosen the o2 for me.

One trick to loosening an O2, because being exhaust..they do get tight.

Put the car on stands, start it and run for a couple minutes. This will heat up the pipe at the O2. Ensure you orient yourself properly and know which way to move the O2. Then a 7/8 and whack are typically what the car doctor ordered.

Be careful of the hot pipes and sensor.

I barely had room under the car when i was under there. I'd most likely be touching the pipe :/

Check engine light came back after about 100 miles. I'm gonna have to try and lift the car higher on stands and attempt to remove the o2 again. definitely need to drill the defoulers out now. If this doesnt work i guess ill have to tune

Im going to revive this 5 months...
I currently have NO CAT. I bought the non foulers, drilled one out, but the O2 sensor is too fat on the end to catch any threads on the non fouler. Also, since the O2 sensor sits on top of the pipe, it didnt look like theres enough room to use both non foulers. frosty, how did you make that work?

The O2 goes on the side of the pipe deleting the "U" shape bend. Pic is upside down and hangers go on the bottom obviously.