Cel issues

Heys guys help me out.I got the dreaded cel PO420.I have reset it twice and ran a bottle of cataclean through it and no luck thus far. The upstream o2 sensor is fairly new. It runs great.What else could I try..Need your suggestions.

 

It is the down stream sensor that reads the cat efficiency .

Might be as simple as a leaking gasket .

Depending on the mileage it might be time for new cats

 

New cat fixed my 420. Downstream sensor could cause the problem but that would be too easy and cheap. It's the cat.

 

My truck has 154,000 miles on it so it could be time.Whats the best aftermarket cats to use

 

I just ordered both cats for my truck. walkers. 400 bucks for both including exhaust and O2 sensor gaskets.

another thing you could try doing is the seafoam intake cleaner.

 

I bought Walker Cats from Rock Auto

 

I put a Flowmaster on but would not go that way again. It works fine but does not have a flange that accepts the pipe lip on the factory system. I had to do a lot of grinding to make it work.

 

Having the same issues. 150k miles. Cel has been on for atleast 5 yrs. No change in fuel economy.i was looking at both cats, muffler and tailpipe from rockauto. Think I may do that. This flow master sounds like ass.

 

For our 1st gens, if the code reads B1 which cat does that refer to?

 

I thought about changing out the downstream sensor since it only cost 61 dollars off Amazon..Then just go from their. Then after that I can find out which cat is going bad..I will also check out rockauto