Whats the part numbers for all of the O2 sensors? I only need one but all three are good to know. I'm going to Oxygensensor.com and I wanna know exactly what to look for.

 

At that site just enter your maxima information and it should show you the 2 types of sensors you need. The first one it shows is the downstream ones and you need 2 of those. The second on it shows is the one in/behind the cat depending on the year of your 4th gen. Bosch are the OEM ones.
I personally wouldn't get the universal ones because you have to wire them up yourself. Which isn't too hard but it can cause problems later.

 

So either of the first three will do? I only need the one at the firewall. I'll get the Bosch.

 

Yeah. Its just that the Bosch one is the stock one.