O2 Sensors - Bank 1 and Bank 2
 

I have a 2004 5.4L with 123000 miles.

I occasionally connect my reader to the computer to see how it is doing and if it is popping any codes. The last time, I noticed that the B1S2 and B2S2 oxygen sensors were not changing their readings and the O2 light on the main screen of my reader was blinking.

I know that this means that I need to replace those O2 sensors, but I can't find anything that tells me which is sensors these are. Google searches come up with very widely different answers.

So which is Bank 1 and Bank 2?
And
Which is Sensor 1 and Sensor 2 on those banks?

Any help would be great.
Thanks,
Gary

Just replace all 4 and be done with it...if 2 are bad the other 2 are not far behind.

While I do plan to replace all 4, I still want to know the answer to this because it might be very useful to know. Say 3 months after replacing all 4 and 1 of them fails. Thanks though.

I don't have my book with me at work...sorry I'm just guessing but I think Bank 1 is drivers side and sensor 1 is up stream.

Bank 1 / Bank 2
 

Bank 1 is Passenger Side, Bank 2 is Driver Side on Ford