P0420

[Wildman]

Ok, it means Catalyst efficency below threshhold...or something like that. Anyways, I was wondering if anyone else has had this and what they did to correct it. I keep getting this code a few days after I clear it out, so it's not a one time thing......

[jabartram]

Ok, it means Catalyst efficency below threshhold...or something like that. Anyways, I was wondering if anyone else has had this and what they did to correct it. I keep getting this code a few days after I clear it out, so it's not a one time thing......

i had the same problem after my high flow cat was installed, i installed an o2 sim, and it has been ok, but i just disabled my bank 2 o2 sensor, with my PT, if all is good, i may sell my o2 sim.

[jackal2000]

PT owns

perhaps your cat is clogged?? i dunno.

[number1alero]

i got the same code when my catalytic converter went bad...it was replaced under full warranty so thankfully it didnt cost anything

[Redog]

IF the cat isn't clogged just get the o2 sim

[Cliff8928]

Yep, basically means that the converter isn't converting enough. Check if your car is still under emissions warranty and you may get it replaced free.

[Wildman]

Nothing is under warranty, it's a 99 with 93,000 miles. Besides, I've got headers in front of the cat, and borla behind it. Looks like I'll be searching for a very short cat. Is high flow really better? or Should I just stick to a regular cat so as to not have any O2 sensor issues.

[jackal2000]

are your headers coated? if it was a poor coating job they could have flaked and clogged the cat. if that is the case, i would be calling s&s....

[jabartram]

Nothing is under warranty, it's a 99 with 93,000 miles. Besides, I've got headers in front of the cat, and borla behind it. Looks like I'll be searching for a very short cat. Is high flow really better? or Should I just stick to a regular cat so as to not have any O2 sensor issues.

if you have headers and highflow cat you will have bank 2 o2 problems.

[Wildman]

are your headers coated? if it was a poor coating job they could have flaked and clogged the cat. if that is the case, i would be calling s&s....

Well I guess we won't know that till I remove the cat. I havnt heard anything like this from S&S headers. I thought that was some of the early TOG headers that had that issue....

[jackal2000]

Well I guess we won't know that till I remove the cat. I havnt heard anything like this from S&S headers. I thought that was some of the early TOG headers that had that issue....

it was, but ya never know.

[Spilner521]

Like others have said, sounds like a bad cat. Get a Magnaflow OBD-II high flow cat to replace it and you'll be fine. I have 3" piping from the turbo-back with a 3" Magnaflow cat and never had any codes.

[Cliff8928]

if you have headers and highflow cat you will have bank 2 o2 problems.

No Alero has any Bank 2 Oxygen sensors..

[Wildman]

Ok, so I'm thinking that maybe I could just hollow out the cat, and put an o2 sim on it to prevent any codes.... In PA for inspection, as long as the cat is physically there, it will pass the visual inspection. And as long as there are no trouble codes, it will pass the OBDII emissions test. Anyone see anything that I am not thinking of in this new plan ??

Theoretically, if I threw on an o2 sim right now, I wouldnt see any codes no matter what condition the cat is in right??

[jackal2000]

sounds right to me. the more expensive route is like jabartram stated, diabling the bank o2 sensor in the pcm with a powrtuner.