jbbrick, I recently purchased a used Mini Winnie on a 2002 E450 chassis. Fuel gauge stuck on full. In working the fault down I discovered the O2 sensor just past the exhaust Y is connected to the factory harness in an unusual configuration. It is connected to the fuel gauge YE/WH sender and ground leads via the factory harness connector. It is easy to get to approx. 4' behind drivers side door under chassis mounted on the main exhaust tube before the muffler. I am still working the issue out with Ford techs, as they are stumped as well. I get the same reading that the O2 sensor is not reading and I have no error codes or check engine light. Ford tech said that the wire color code and pinout I gave them does not match the factory diagram. This is the orginal factory harness, never modified. They state that the O2 would not work, wired the way I informed that it was. I am still working the fuel gauge issue, but it appears to be intertwined with the O2 sensor not being properly wired from the factory? When I disconnect the O2 sensor I still do not get an error code or check engine light! I believe that my problem with the fuel gauge started when the previous owner replaced the O2 sensor with an aftermarket unit due to it not reading. If the wrong O2 sensor/wire pinout was installed it may be creating the problem with my fuel gauge. I will keep you posted on my progress today and if it sheds any light on your O2 sensor issue.
