Zenpal,

I am new to this forum. I have the same issue with my 2000 f150. I have a post in the truck section, 1997-2003. (Martinjose) Based on the response I am getting sounds like the O2s sensor is bad. You can visit my post. Hope this gives you some answers. I am going to replace the upstream 02s in my truck.

Let me know what you findout.

Martinjose.