check engine light

hi all
with my 96 ford windstar , ive been having trouble with the CEL .
i had it checked out and was told the oxygen sensor was bad.(bank 1 sensor 1). i had the sensor replaced and awhile later the light came back on and then i was told it was another sensor.(bank 1 sensor 2).........the sensor just behind the cat. convertor. i didnt get this one done yet.
however, i find that the only time the CEL illuminates is when i have half a tank of gas. is this a sign that maybe it could be something else?
after i fill the gas tank.... the light soon goes out and stays out till i burn half a tank....witch doesnt tane very long.... but thats another story lol
thanks for any help.

It is common for people to have their codes read and then be told that they have an O2 sensor problem. Replacing the sensor may shut of the light trmporarilly but it often returns.

I think O2 sensors are the scapegoats. Often they are reading correctly and the PCM is getting bad data from them simply because there is something wrong upstream.

Now having said that...........You really need to get the actual code numbers. Post them back and one of the many folks here will help you find the root cause. It could be the sensor but then again it could be a lot of other things. I would be very skeptical of anyone who reads the codes and instantly claims they know the root cause. A bad reading is only the effect of the problem.

Your gas tank correlation could be related.

yeah, the 02 sensors are scapegoats sometimes, especially for p0171 and p0174 codes. find out what codes are stored in the computer