[noppe180]

went and got it the code checked P0420

the PCM has determained that the catalyst system efficiency for bank 1 is below threshold for the current engine operating conditions.

its says causes:
1. catalytic converter defective
2. engine misfire or running condition
3. large vacuum leak
4. engine oil leakage into exhaust-valve guide seals, piston rings.

havent noticed and motor running different. what would cause #4

[noppe180]

is that the front o2?

[MustangMatt96GT]

I think that your cat is bad! I guess its time to upgrade to a O/R h-pipe!

[HMUSN]

its just an 02 sensor man.


and dont pay to have it fixed... its only one connection and one bolt./.

[MustangMatt96GT]

You sure its just an O2? If it is they are simple to do!

[noppe180]

a bought a used bassani xpipe w/ high flow cats. low price. but i live in tx and emission testing is wierd. so just get a o/r w/ the o2 sensor things

[noppe180]

i think i have a leak from the header to the pipe. i bent my tip so been waitin to get it all fit right.

[MustangMatt96GT]

Its just an O2 sensor if HSMUN is correct! My guess would be the O2 closest to the engine on the drivers side exhaust by looking at the code, but I could be wrong on the part being closest to the engine. But it is definatly on the drivers side if it is an O2 sensor! Wait for casper to say something about it or just take the code to your parts dealer and ask them what they think you need!

[MustangMatt96GT]

If that leak is on the passenger side then That could be it! Because the code reads P0420- Catalyst System Efficiency below Limit - Bank No 1. Efficiency below limit may mean its not getting enough air to test!

[ujslost]

I believe this is gonna be the rearward O2 sensor. But Im pretty sure like HSMUN said its an O2 sensor. I have the same thing on mine since I cut the cats off and havnet installed MIL eliminators yet.

[Casper98GT]

blah blah blah...its not a 02 sensor. Its a cat efficanty code. If you had a bad o2 you would have a 02 code of some sort. Youre leaking through air in youre 02 system. youre 02 sensors dont like what they see so they think the CAT is the problem. If you just put on a pipe, check for leaks first. Then correct them and clear the code.

[HMUSN]

Originally Posted by noppe180 a bought a used bassani xpipe w/ high flow cats. low price. but i live in tx and emission testing is wierd. so just get a o/r w/ the o2 sensor things

ahh ok.. you didn't say that at first.

i agree with casper then.

check for a leak .. that is probably what is causing your 02 sensor to freak out.

i though you had stock pipes.

[noppe180]

hope it works i gonna take it to the muffler shop cuz i bent a tip and it should be here in a week and MAGNA FLOW cat systems wow to get a tip...... i ordered 1 .025 small all the way around send it back they lose it... then he tells me i got to go a muffler shop to have them size it. i was like wtf.....

[noppe180]

so its a vacuum leak if its the prob a.k.a. exhaust leak

[MustangMatt96GT]

It is an exhaust leak!