Okay, first let me say replaced both both O2 sensors on a 98 dakota. The downstream sensor just gave me a code. The cat is not very hot at all after a 10-12 mile trip. I'm assuming it's bad. My prognosis anyway since I unplugged the back sensor and still reading 1000mv. Unplugged the front sensor and that went to 1000mv. Plugged in the back sensor, read 1000mv and the front sensor plugged in shows a varying voltage like it's suppose to. My problem is I need to drive back to Jersey from Florida tomorrow, hoping I should be able to do this drive and I'll replace the cat when I get home....what do ya all think? Thanks!

 

If the only code that is showing is for the rear o2 sensor then you'll be fine for the drive, you just may not get very good milage. I drove my truck for 2 years with that code, till I cut out my cat and the insides were pretty much gone. Then I put 2 non-fouler on the sensor and only had it trip a code a couple times till I replaced my muffler and haven't had a problem with it since.

 

My 97 my rear "Post Cat O2" doesnt even work.. I know it does not because when my cat blew out when i had a no fire condition.. it never tripped anything... no CEL of any kind.. but my truck drives the same in either case.

The Cat not being very hot really does not tell us much.. it could be anything really.. most of the time a bad cat will result in one side having higher pressure than the other side because its plugged up and will be uber hot.. and can make it glow as well.. because that pressure/heat has no where to go.. but also your not gonna go anywhere quickly with a plugged up Cat.. but on the flip side a burnt out CAT your gonna smell like an old Ford/Chevy/Dodge pickup truck...