回复：关于Oxygen sensor

There will be oxygen sensor(s) right after the manifold exhaust. Inline engine has one, V-engine may have two.
There possible will be 1 oxygen sensor right after the catalytical converter. Single exhaust pipe may have one, dual pipes may have two.
Check those two locations will tell you how many HO2S you have.
My sense, if you can DIY, change all of them. I do not think one from dealer is much better from Autozone or general parts stores.