O2 sensor removal question
 

There are two sets of wires that go to the O2 sensor. One is a three pin and the other is a round connector. The three pin pulls straight out but the round will not budge. Does it just pull straight off or is there a trick? I don't want to damage anything. Please let me know how to disconnect this connection please! thanks. Joe

Peel/roll the rubber protective cap back, then pull on the wire.

The Cap'n

Pull straight out, the part mounted to the chassis is very brittle, try you best not to damage it. It has seen allot of heat. Try some spray lube then pull gently

I would probably cut a slit in the rubber boot, then gently peel the boot off. Otherwise, you may crack the insulator plug, as already pointed out.