I replaced the exhaust on my 2006 Ram including the cats and put a catback system on it. Since then, it constantly is throwing the following codes:

P0137 - O2S Ckt Low Volts 1 2
P0138 - O2S Ckt High Volts 1 2
P0420 - Catalyst Efficiency Below Threshold Bnk 1
P2096 - Post Catalyst Fuel Trim System too Lean Bnk 1

Is this all from a faulty O2 sensor or do I have a bigger problem?

Thanks!

Are they aftermarket high flow cats? Did you replace the ex manifold gaskets?

Aftermarket cats from Rock Auto. Dealer ordered and installed them so I assume they changed the gasket as well.

Apparently they are stock replacement cats? I have walker replacement cats on my 06. BTW, the gaskets I was referring to were from manifold to the head. I doubt they touched them. I had the two codes P0420 and P2096 prior to replacing my complete exhaust. I even put in new mopar sensors. I starting getting the same codes again after. I found out my ex manifold was leaking. I replaced the gasket and the codes went away. After awhile the P0420 code came back. I tightened the bolts more and the code went away again. I believe my manifold is warped and that is causing my problem. Are you hearing a ticking noise? If you had no codes prior to the install I`m wondering if you have a exhaust leak at where the head "y" pipe meets the manifold or somewhere else before the cats. Was you Y pipe a two piece or one piece like factory?

Yes, stock replacements and the Y pipe is a two piece. I'll check all the bolts to ensure all it tight. I don't see/hear any leaks or ticking noise.

I am surprised they reused the sensors. The front two generally almost get welded in there and they strip the threads when removing.

Should I just replace them and see?

It is really a shot in the dark. If you do replace them use mopar ones. Aftermarket ones can be a issue sometimes. Do you not want to take it back to the dealer for them to check out?

Aftermarket cats can sometimes be an issue. They fail to contain enough precious metal to function correctly. Those 02 codes are post cat codes...I had an 04 that had both post cat 02 sensors fail(along with a ton of other stuff)Good luck!!