i would like to know ; where is the speed-distance sensor on a plymouth minivan

There is no per say distance sensors, there can be ABS wheel speed sensors and there is an transmission output speed sensor used on most FWDs for speedometer input which is also used for the Odometer that you may be referring to as distance sensor. It tracks wheel rotation not distance so if tire was slipping in ice, snow mud ETC... it would show more mileage even though the vehicle may not have moved