1997 Ford Ranger with EGR SYSTEM PROBLEMS, PLEASE HELP!!

I have a 1997 Ford Ranger with a 3.0 litre engine. The check engine light says on. I have replaced the vacuum swith, the spark plug wires, and have checked the egr valve and it is o.k.
I have been told there is a sensor that controls the vacuum switch, Do you know where it is located?

When we hook the vehicle up the code reader, it reads "Insufficient recirculation of exhaust gasses".

Do you know what this might mean?

Any help would be appreciated.

Thanks

Check out expedition forum there is a link by RickMN that explains how this system works and tells you how to perform basic checks. DPFE sensor is usually(not always) the culprit for this particular code.

Thanks Carlos, that was very helpful. Much appreciated.

99mallard