O2 sensors are driving me crazy!

[debate]

The service writer told me that Ford warranties the emissions system to 60k miles.

 

[Mjolnir]

the barrels of the O2 sensors are ceramic. if they got banged around during removal or installation they could get a small hairline crack in them, rendering them inoperable. I had this issue with mine, took me forever to chase it down. Finally got one of the techs at the mod shop to admit he dropped one trying to put it in. replaced it and everything worked after a 50 mile reprogram drive.