p0420 code

[moparmarv]

I have a 2008 dodge advenger that keeps giving me a 420 code catalyst efficiency low bank 1 I have replaced the 4 o2 sencers and the rear cat but it still throes the 420 code any suggestions thanks. it has the 2.7 v six

[JOHNBIGDOG]

I know nothing of dodge.

I would have to say that a scan tool watching the O2 data stream would help a lot in this situation to see how well the cat is performing.

[Jeremy airjer W]

How many miles on it?

What engine?

Where did you get the catalytic converter?

[moparmarv]

2.7 v 6 108000 miles magnaflow converter

[leech~~]

Sounds like your Cat is getting packed up. Not much you can do "legally" to fix that but to replace it!

[bjhag]

I agree with Leech, you probably need the exhaust manifold cat. convertor on the affected bank. Repaired quite a few cars and trucks this way.

[Jeremy airjer W]

P0420 is a bank 1 cat code. Bank one is the same side of the engine as the number one cylinder. Did you replace the cat in between the two sensor on bank one or did you replace the secondary cat. If you replaced the secondary cat than there was no chance of that fixing it.

I'm pretty sure there are three cats on this one?

[moparmarv]

I did replace the cat on bank one between the two o2 senders on the rear manifold about 3000 miles ago

[Jeremy airjer W]

Do you know what brand of 02 sensor you used? It is highly unusual to have to replace all of them around the same time. Not all O2 sensors or cats are, created equal. You may have been on the right track with a new cat but the cat you installed is not capable of producing the desired results.

I would have to agree with my brother on this one. It's time to see what the data is telling you. If the downstream O2 is switching just as much as the upstream than the cat is not doing its job.