Are the O2 sensors the same and the wires different sizes or are the O2 sensor totally different?

Did a nice search on the PO421 code. What a PITA.

 

It's mainly the harnesses that are different if that is what you are asking. The ecu reads them totally separate though.

 

Yeah, so I did a nice seafoam treatment and the engine light went out all by itself. Light came back on a few days later. I ran the codes again, this time I got the PO421 and PO300, the o2 code did not come up. I did install new plugs and they were not NKG. Is this a problem. I can put the old plugs back in if needed.

 

I double checked ignition wires and one was not snapped onto the plug. I will see if this code resets. How long does PCM take to reset?