Im working on my father in laws truck for him, its an 04 Expedition with 225k miles on it. In the last 6 months Ive replaced a lot of things. In April I replaced all 3 Catalytic converters, he didn't have money for o2 sensors so they weren't done at the time (they were bad). Then in June the heater valve went I replaced that, Last month I replaced all 3 O2 sensors and the truck ran great I was shocked by how smooth it and and the power the thing had. Then 2 weeks later the intake cracked at the right side water port in the front. So when that was off we replaced all the vacuum hoses and elbows, all the injector O rings, sprayed the bottom of the injectors with carburetor cleaner to get the crud off, changed the ORIGINAL spark plugs, replaced 2 bad coils, cleaned the throttle body (with throttle body cleaner),cleaned the IAC, and wiped out the ports on the head with a rag and brake cleaner. We got it back together and the truck ran phenomenal! Sunday night he had another coil crap out. I replaced it yesterday and we reset the check engine light. Now today he called me and said he's getting code p2196 and P0420. Does anyone have any idea why? I was thinking maybe from it running bad the O2 got gummed up and now the crap has to burn off? Honestly Im at a loss can you guys help us out?

 

Your problem can be that you replaced 3 O2 sensors and the truck has 4.

 

I made a mistake all 4 O2s were done. Sorry about that.

 

Are you 100% sure you plugged them back in good and solid on the passenger side?