What is the little white module on the top of my transmission?

Does anybody know what the little white module with the electrical connector in front the the TRS is on top of the transmission on my 96 3.8 Windstar, and what it's function is? Reason I ask is today my tranny started slipping so bad on the highway I had to get off early. When I got off, it was slipping so bad I couldn't get up the hill I stopped on. I unplugged this module and I had third gear. So I moved my gear selector to 1 and I was in second gear. Then when I moved it to "2", it very smoothly shifted into 3rd. I continued running my errands like this and didn't have any more problems.