Where are the up and downstream O2 sensors located?

 

Right behind both manifolds and the other two right before or in the back cats

 

BTW this job will be done on my '02 f150. OBD codes p0171/74 was thrown.

 

Rocko, don't spend your money on O2's just yet. P0171/174 are rarely from bad O2 sensors.

Post up some info about your truck so we can walk you through it.

I see it's an 02
what motor
maintainence history
miles
what if any mods

Most common for those codes are air leaks.

 

Yep, usually vacuum line leak off PCV valve or back of intake manifold. I had those codes, had a split vacuum line off PCV valve. 7 dollar fix. Listen to your truck with engine running, pinch vacuum lines and see if idle changes or leak is heard.

 

Most common for those codes are air leaks.[/QUOT
5.4L, regular maintainence, 168k, K and N CAI (installed by previous owner), new PCV valve, new plugs and new ignition coil on one cylinder.

 

Also blend door and heater core replaced.

 

Check evetything on that PCV system all the way from the rocker cover to the the famous elbow for any leaks. Also since you have a K & N clean the MAF and check all the connections on the CAI.

Any air entering the motor after the MAF can throw those codes. Also an exhaust leak close to the O2 can do it, but is unlikely in your case because you are showing lean on both banks.

Betcha the parts store guy said to buy new O2's, huh?

Check that stuff first and let us know how it goes, good luck.