P0420 and P0430 cat codes keep coming back

[JuddW]

2014 3.5 Limited: Keep getting P0420 and P0430 codes. It started with just bank 2 at first but now it is both. I have replaced upper and down stream 02 sensor on bank 2. That didn't fix it and than the bank 1 code for the cats started coming in. So I broke down and drop $1100 to replace both cats. The codes came back in on both banks. Anybody have any ideas?

 

[CNors1103]

2014 3.5 Limited: Keep getting P0420 and P0430 codes. It started with just bank 2 at first but now it is both. I have replaced upper and down stream 02 sensor on bank 2. That didn't fix it and than the bank 1 code for the cats started coming in. So I broke down and drop $1100 to replace both cats. The codes came back in on both banks. Anybody have any ideas?

Are you using a remote start?

 

[JuddW]

Are you using a remote start?

Yes

 

[FLYNLW]

2014 3.5 Limited: Keep getting P0420 and P0430 codes. It started with just bank 2 at first but now it is both. I have replaced upper and down stream 02 sensor on bank 2. That didn't fix it and than the bank 1 code for the cats started coming in. So I broke down and drop $1100 to replace both cats. The codes came back in on both banks. Anybody have any ideas?

I’m struggling with the same issue. I have the same model ‘13. I had cracks in both manifolds hence replaced them and replaced the upstream and downstream O2 sensors. No codes before I started the replacement work, now I have P0430 and P0420 codes that keep coming back.

While doing the work I replaced the spark plugs, throttle intake gasket and bank 2 valve cover gasket for good measure.

I had to replace the gasket between the collector exhaust pipe and the bank 1 manifold lower flange as the new manifold has a slightly different angle to mate up to. I could hear a puffing exhaust sound after a weeks driving. The manifolds I used were FVP brand from Rock Auto. I thought this would fix my code problems but… NO.

I’ve since replaced the upstream O2 sensors again today after getting multiple opinions from mechanic friends. Just 2 drives in tonight the codes have come back again.

I’ve checked all related fuses, no problem. One thing I have noticed with the OBD2 scanner is I can’t see any voltage readings from the Upstream O2 sensors since the replacement work.

214000km, driving fine otherwise. I’m still searching for the answer to these pesky codes.

 

[CNors1103]

Yes

I narrowed my similar issue down to the remote start. Clear codes and the do not use the remote start and see if the codes return. This has resolved my codes from coming back. I posted my exact problem on this forum, but no one has replied as to what could be related to the remote start that could be causing this.