Blackhawk4600

I want to replace the O2 sensors on my '04 (non-heritage) and I found some threads that talk about which ones to use ... but nothing on how many to order. It is noted that the Motocraft is best bang for buck but how many "FRONT" sensors do I need and how many "REAR" sensors do I need?

I ask because O'Reilly Auto Parts says I need (2) Upstreams and (2) Downstreams if I order Bosch but the Motocraft says only need (1) FRONT and (1) REAR ... Does this mean they come in sets?

kevhead75

There are 2 sensors per bank so 4 total (2 fronts & 2 rears) Stick with motorcraft. Tasca or Rock Auto usually has good prices on them. The front 02's are the ones you want to replace as they are the ones monitoring for the pcm to make changes to fuel trims and etc. The rear o2's only monitor cat efficiency and usually do not need to be replaced unless they are damaged some how.
Now changing the fronts are the fun part. You will want a low profile 7/8" o2 socket and I had better luck using a long 7/8 open end wrench getting the passenger side out. On the passenger side it may be easier to remove the rear o2 so you can get your hand up near the front one to unplug it. You may have to bend the heat shield slightly to make more room. Make sure you use a little anti-sieze on the threads when installing.

Blackhawk4600

Thank you!