O2 sensors in 3.0 litre engine

I have a 3.0 litre Windstar 1997 made for Europe. I just found that I don't have O2 sensors on exhaust pipe. I have only the front ones on the manifold. The Mitchell shows four O2 sensors, the OBD2 scanner also shows 4, but the rear ones show 0V all the time. At the exhaust service they told me that this could be possible, especially in Europe version, but don't really believe it. Could it be that smbdy removed them?

Gobowiec :-)

I cannot comment on configuration for Europe.....is out of my knowledge....
I CAN tell you that ALL 4 sensors on my '96 are actually in the exhaust pipe.....the part called the "Y" pipe. The Y pipe is a 1 piece assembly that includes the pipes from the exhaust manifolds to the catalytic convertor(s) and the pipe that goes from the catalytic converter(s) to the flex pipe that is in front of the big square muffler.....which is right under the first row of seating...... My 3.8L has 2 converters......then the pipes merge into 1 pipe, just in front of the flex pipe.
As you mention 4 sensors.......that would be for the 2 catalytic converter arrangement that I described.
If you only have 1 catalytic converter......you will only have 2 oxygen sensors.
The sensors that are before the catalytic converter are used for monitoring the fuel mix......lean to rich......and that is what the computer uses to control the engine.......as in, how much fuel to spray through the injectors.
These are called "upstream" sensors.

The sensors that are located AFTER the catalytic converters ONLY monitor how well the catalytic converters are working.
They have nothing to do with the fuel mixture.
They will light the Check Engine Light if they are not working.....and the failure will be "catalyist efficiency".
They are required in the USA to make sure that the emissions systems are working. (along with a few other sensors).

I have a picture in my pictures (the link in my signature will take you to them) showing the original "Y" pipe.....and the Walker "aftermarket" unit that I installed.

If someone has removed an oxygen sensor......they will have had to plug the threaded hole. The threaded hole is basically a big nut welded into the exhaust pipe. Very obvious.......if you know what you are looking for.

Thanks wiswind,
I have those nuts, but no O2 sensors. My only two sensors are mounted higher than yours, comparing to your picture 8 on page 1. I'll leave it as it is, the car passed tests. After all it's just for control, I just wanted to know if somebody removed them, or from new it had only two sensors.

Gobowiec :-)