My 01 3.0 is the same as yours. There is something in that receptacle in the bottom of the tank (I just replaced mine as well), but it is not hooked up. I cannot find a lead that would plug into it either. On the other hand, I have never had coolant level low enough to test the functionality of the low coolant light, so I don't know if it works or not.

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2001 E53 3.0 5pd