wiring a stero

I have a 2001 Windstar and I rescently installed an aftermarket stero into the van. The stero works on only my front speakers now. I replaced all of the speakers with Pioneers. I have no sound on my rear speakers that are located on the door. How do the rear speakers work? I couldn't find any wires that go into the door. Does it have something to do with that 4 pin contact that is on the door? Any solutions? Thanks

I have a 2001 Windstar and I rescently installed an aftermarket stero into the van. The stero works on only my front speakers now. I replaced all of the speakers with Pioneers. I have no sound on my rear speakers that are located on the door. How do the rear speakers work? I couldn't find any wires that go into the door. Does it have something to do with that 4 pin contact that is on the door? Any solutions? Thanks
Yes, the pin contact, feed the speakers ( those in the sliding doors) and the power door lock. You can remove the pillar trim to see and follow the wires from the radio. I can provide the wire color if you need it.

If you could supply the wiring colors that would be greatly appreciated. Is there ever any problems associated with the pin contacts?