in june i purchased a zzp downpipe with magnaflow cat, in july i installed it.. now nearly 5 months later i have been getting P0420 codes.. no leaks and o2 sensor is functioning correctly. I would like this issue resolved. I called but didn't get an answer.

I throw the same code every once and a while with my Vibrant dp. They told me that it would do that if you go WOT frequently because it is designed to flow so well.

did you make sure the cat is still good? if everything is running ok i wouldn't worry about it. delete the code and see if it comes back.

Haven't installed it yet but this is what I am going to try. I measured the fit and will be really close to fit, but I think with some ingeunity I can get it to fit and I will keep you posted if it works or not.

http://www.voodooboost.com/performance_accessories/O2_Simulator/

Maybe zzp can try and come up with one that is a direct fit!!!

I throw the same code every once and a while with my Vibrant dp. They told me that it would do that if you go WOT frequently because it is designed to flow so well.

it shouldn't happen mainly because it flows well. if the light comes on the rear o2 is noticing that the cat isn't doing its job...I just wish i knew how long this code has been pending.

did you make sure the cat is still good? if everything is running ok i wouldn't worry about it. delete the code and see if it comes back.

yea the cats fine.. deleted the code before i made the post while i checked over the rest of the components and double checked for leaks.

Think i might just disable it with HPT

well...cleared the code twice now and sure enough it comes back. freezeframe data is all good.

its not the high flow, this cat is shot after 4,000 miles or so... GAY... guess i'll stick with random technologies from now on.

I had a CEL for about two days with my new header then went away but sucks it keep coming back....but all-in-all is it worth the money minus the codes?

Delete the rear O2 with HP tuners......

I had a CEL for about two days with my new header then went away but sucks it keep coming back....but all-in-all is it worth the money minus the codes?

certainly worth it if it didn't have issues.... with the codes i don't see it worth it because then i might as well just be catless, but i don't like drawing so much attention to the car in this state due to them pushing the "every modified exhaust is illegal" without it being a law... With the high flow and gmpp..it isn't loud at all

The cat isnt operating anymore, mine threw the same code so I went to an exhaust
shop and had them pull it out and it was completely empty.

i threw this same code.. i'll clear it and it just comes back. got the ZZP set up (midlenth header & downpipe with high flow cat) .. probably just going to get the rear o2 sensor deleted with HPT

i'm throwing this code with my new RT cat/downpipe, been on my car for 250 miles or so now and the code came on after 150 miles. I do have a leak between the downpipe and header which i'm fixing tomorrow with a new gasket so i'll see if that fixes it.

Got the spacer installed from the website I posted and no more p0420. Had to cut a 3/4" square hole in the metal to get it to fit. Reset the code drove around with the scanner plugged in until it ran the checks and no more check engine light. Have to thank Baddass (lewis) for his time and tools.

i'm throwing this code with my new RT cat/downpipe, been on my car for 250 miles or so now and the code came on after 150 miles. I do have a leak between the downpipe and header which i'm fixing tomorrow with a new gasket so i'll see if that fixes it.

that would certainly cause the cel as its pulling in unmetered o2 throwing the readings off

It isnt un common for a high flow cat to set a rear 02 code occassionally .

if you tune your car with hptuners than the person that does it can get rid of the code for ever.

I have the zzp mid-length and never had a prob until the car is was tuned, now when I really hop on it it throws a code. everyone I've talked to about this says it happens all the time with high flow cats since they don't really do as good a job as a stock cat does (as far as emissions goes). I don't think the cat is bad, it's just not filtering the o2 as much. the spacer should do the trick, (btw...try screwing to spark plug non fouler together and drilling one of them out (it's the same effect and costs 1/4 of the spacer)

call zzp tell them they failed to mention it would cause a cel theyll hook you up with a custom tune for cheap that deletes the code or they will delete it for free or 20 dollars or somthing if you send em your ecu... this is what they were willing to offer me anyways and i went with a custom tune and they only charged my 100 dollars

I have the zzp mid-length and never had a prob until the car is was tuned, now when I really hop on it it throws a code. everyone I've talked to about this says it happens all the time with high flow cats since they don't really do as good a job as a stock cat does (as far as emissions goes). I don't think the cat is bad, it's just not filtering the o2 as much. the spacer should do the trick, (btw...try screwing to spark plug non fouler together and drilling one of them out (it's the same effect and costs 1/4 of the spacer)

what he said will work confirmed by me... ccp

see my tuner said he "would" delete the code if I really wanted him to, but that he wasn't sure if it would show in the scan they run on the ECU for emissions. anyone know?

same prob...zzp catted combo/3"DP

was gonna buy the anti fouler today but didnt know the effectiveness

cat could possibly be bad after the 5 months on here...my stock cat shelled out and when it did i had similar symptons

been trying to fix header/DP flange leaks for about a month or so know but now that its doing better it throws codes

replaced the 1st 02 sensor due to insuffificient switching codes now it throws 420

i think exhaust leaks pre cat with my mods melted the cat again...damn rich AF mix

gonna try washers to space out the second 02

and if the cat is trashed then go catless again