I have a 1999 Dodge Ram 1500 4x4 5.9L engine and I keep getting PO420 as the code. I know what it means so my question is could it keep coming back because it is searching for the catalytic converter. It has one but I busted all the stuff out of because it was clogged up. I really didn't feel like replacing it because I just had a new one put on it about 2-3 years prior and it got clogged again. I went ahead and replaced both the pre and post O2 sensors. I may eventually put another one on there but I only drive it maybe once a week or if I have to pull my trailer or haul something. It runs fine and my gas millage has gotten worse but I expected that when I took the catalytic converter off. Any help or advice that anyone has that would help me out would be greatly appreciated.

 

Welcome to the site. Check out the Ram sections.
FF

 

Welcome to DF. Head over to the 2nd gen Ram section and post your question. Here is the link:

https://dodgeforum.com/forum/2nd-gen-ram-64/