P0420 error; Thinking about replacing CAT
 

Hey guys,

I have a 05 Shinka, and a few days ago my engine light came on on my way to work, so i ran over to Advanced Autoparts after work and grabbed their diagnostic machine to plug in and see what was up, got the P0420 error "Catalyst System Efficiency System below threshold Bank 1". I started a new job this week also so i haven't had time to go to the shop and really get it checked out.

I know its either the O2 sensor or the cat, and I have a feeling its most likely the cat....i have read around on the forums quite a bit, but I wanted to know what you guys thought in case i missed something....

Assuming its the CAT, i was thinking of getting the RP ‘Supercat’ Mid Pipe @ http://www.rx7.com/store/rx8/rx8exhaust.html thoughts?

and any other ideas? sadly iv gotten a good amount of miles, sittin at 85k now, and alot is piling up that i wanna do after my first couple paychecks from this new job.....compression test, new plugs and wires.... was sort of looking at the BHR ignition system but idk for sure.

Thanks for the help

I got the same code. I cleaned, and ended up replaceing the rear 02 sensor... (80 dollars) with no effect. It is most likely your cat and i would urge you to not waist your money and just take care of it. You seem to have alot of good ideas planned out for your 8, and much like myself, a failing cat kinda poops on all the stuff you would rather spend your money on. For now I picked up the ap midpipe, its got duel resonaters and its only 200$. Wont harm your car like a clogged cat and the packing should hold up long enough for you to spend some money on other improvements. Just my thoughts, ill keep the pipe until it loses its tone, and then i will most likley upgrade to bhr and a catback system.

you could just save money and gut the oem cat since you are out of warranty anyway.

I agree with your assessment ... it could be either the CAT or the Rear O2

What I would do (don't know where you live):

1) Where I live they actually do a sniff test. I would pay the 28 dollars and see if I pass the sniff test. If I fail then I know it's a bad Catalytic vs a fail Rear O2

2) If I passed sniff test I would replace Rear O2 ... fairly cheap and easy ... I suggest and over night dose of penetrating oil first.

3) Consider your pollution laws ... the RP Super Cat will not pass emissions in Ontario Canada ... well it didn't on my 2005 MT when I was NA

Best options depends a lot on where you live. You didn't say, so pretty hard to answer.

I live in south dakota, dont have to worry abouth emission tests really.

What do you mean by the sniff test? i also have a p0420 bank 1, my rear sensor is new (like a few months old) and the car is running very rich, it smells awful. theres also a hint of blue smoke from the exhaust, im hoping a new wideband sensor will fix this. what do you think?

The sniffer test is where they hook up a hose to or near the end of your exhaust and measure the pollutants that it produces. Some states do this while others do the obd2 test.

if its actually throwing a p0420 code the cat is probably already hollow, i would actually wait to change it until AFTER a compression test, the cats are fragile on these cars, so you'd want a healthy engine first.

imo....

the cat is basically the only emissions part on the car, so if its bad/missing/not working the car will smell bad.

i would find a scanner and watch the o2 sensors, if yours works (80% chance it will) you need a cat.

why am I the only one to notice that this thread shouldn't be here under aftermarket performance?

Probably because the moderators are likely too busy closing threads to make sure they have the last incorrect word

Pretty sure you only get this code when the cat falls below the minimum emission level threshold, not for a bad rear O2 sensor

i think so too. i would expect a bad o2 to throw a bad o2 code, maybe along with the cat code, but i have seen stranger things than a p0420 being an o2!

my experience with actually having to smog these cars is that they fail the emissions tailpipe test way before it throws a code. :sad:

A bad or failing rear O2 sensor is not listed as a possible causes for a P0402 code, it's just uninformed people using their typical 1+1=3 guessing game theory


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