Hey guys new to the forum. I have a 96 dodge 2500 with the 5.9 magnum. I just had a cat delete going into an xpipe to a side pipe coming out right in front of the the bed. Now my question is, is the downstream 02 sensor really necessary for the truck to run correctly or is it just there to tell me the cats are bad?

 

It's just there to monitor the cat, but, the PCM may be offended if it isn't there... Some folks just tie-wrap it to the frame, and the PCM is happy. Non-fouler trick is another option. There are threads about that in the 2nd Gen Ram FAQ/DIY section.

Welcome to DF!