reoccuring P0420 code

**skipfleming** · 09-29-2011, 09:34 AM

Hi I'm new here.. i was hoping that someone could help me,, I'm getting a reoccuring P0420(left bank Cat converter below efficiency) I have a 2002 Trans -Am WS-6 Automatic, with A K&N air filter,and a header back exhaust with High flow cats,, I've changed both of the left side O2 sensors but that only made it worse.. the Exhaust has the bung spacers for the O2 sensors. I've been told that it could be the MAF sensor.. or the TEMP sensor could be at fault,, does anyone have any suggestions,,P.S. I still runs like a striped ass ape even when the light come on .

**Goldcuffs** · 09-29-2011, 04:26 PM

You will never get that code to go away with high flow cats. Go to WS6store.com and get some O2 simulaters and that will fix it. Had the same problem.

**Cutlass** · 09-29-2011, 07:11 PM

^^^True. Although I didn't think anyone sold O2 sims anymore. If you can't find sims, find a tuner to disable the cat converter codes.

**0rion** · 09-29-2011, 07:17 PM

having it tuned out is the best way to go anyhow......sims weren't real reliable. Like you've already observed....it won't effect your performance.

**Ain't Right** · 09-30-2011, 10:38 AM

Love how 420 code is for the exhaust...get rid of tyat K&N filter or you will have a MAF problem before long

**0rion** · 09-30-2011, 11:14 AM

Originally Posted by Ain't Right

Love how 420 code is for the exhaust...get rid of tyat K&N filter or you will have a MAF problem before long

not necessarily.....I've ran a K&N for 12 years with zero problems with it. You have to know how to oil them and include cleaning your MAF as part of your routine maintenance which it should be K&N or not.