p0420 (open exhaust)

[junkey_chan]

my car is throwing this code p0420(cat system efficiency below threshold, left bank) did the converter went out? is it some thing to worry about? and shood i not run open exhaust any more? tnx

[96greenmachine]

Re: p0420 (open exhaust)

do u have a regular cat? or gutted? and what kind of open exhaust u got? cut out or strait pipes? if a cutout where is it located?

[junkey_chan]

Re: p0420 (open exhaust)

ah sorry i just unbloted it from right behind catalytic converter, it is stock cat, 2000 3.8 auto

[96greenmachine]

Re: p0420 (open exhaust)

still have the post o2 sensor? if so im thinkin the manifold o2 on the left side went out...mine did the same thing

[junkey_chan]

Re: p0420 (open exhaust)

cool will check it out, what harm could it do if I leave it like this and shood i put back my exhaust?

[96greenmachine]

Re: p0420 (open exhaust)

well idk bout your inspection process but it wont hurt anything except for having to have a muffler...but i would replace the 02 at least...i wouldnt worry bout ur exhaust, unless they check for a muffler when u get it inspected

[loser]

Re: p0420 (open exhaust)

if you took the exhuast off right after the cat, the post car 02 sensor is probally just danging there, and of course that will set a code.

the code wont hurt anything, i dont know how long id drive like that, thats probally anough pipe where cold air wouldnt go up it ( shocking valves isnt good ) but it has to be stupid loud.

[JohnnyC]

Re: p0420 (open exhaust)

I had a similar setup - stock manifolds, open cat but I left the S-pipe and I drove it that way for close to a year. Stupid loud is an understatement, it was shrill. Never burnt a valve though.

[Loochy88]

Re: p0420 (open exhaust)

with the sensor behind the cat unpugged, you will need either an O2 sim or you need to put the pipe w/sensor back on. you will fail emissions in that situation if you in fact have emissions testing

[junkey_chan]

Re: p0420 (open exhaust)

sensor right behind cat is on, i took off right after the sensor :) i guess i need to try and change it out

[DAS BOOT]

Re: p0420 (open exhaust)

where did you take it off after the CAT?

did you cut it right behnd it or just unbolt it from the factory spot?


If you unbolted from the factory spot, it is unlikely you are tripping the code because of it.


I clogged my stock cat @ 35k, and the replacement one at 70k. I just gutted it and put it in and HPtuned it out.

[junkey_chan]

Re: p0420 (open exhaust)

If you unbolted from the factory spot, it is unlikely you are tripping the code because of it.

i did it from there. o2 sensor bad? like the other guy said?

[DAS BOOT]

Re: p0420 (open exhaust)

to be honest from my experience...

Its the CAT thats bad, not the sensor. i coudl be wrong but jsut giving advice before you dump like $75 on a new one.

If your exhaust is stock and its less then 7 years 70k miles I believe they will replace your CAT under warranty.