I am passing this on as I found this error on my truck, and after buying a shiney new O2 sensor, found out it was something else.

I saw the check engine light, and decided to extract the codes to do a self-repair.

Of course I pulled a lean-code out and the indication was the O2 sensor was giving bad results.
(forgot the actual description)

Long story short, I have a brand new O2 sensor in my manifold right hand side, and ended up replacing a little short rubber elbow in my vacuume lines to repair a leak that was causing my error code.

Moral to the story?.. the error code isnt an indication of the problem, just an indication of a sensed fault. Check your not-so-obvious causes before buying what the auto parts guy is more than willing to sell you.