I've got an '07 Escape XLT 3.0L V6. I just ordered and installed a class III hitch and a wiring harness that plugs into the 4-pin round plug found behind the left rear tire under the bumper cover. I discovered first that the wiring harness wasn't working at all. Then I tested the plug in the bumper and it has no power either. Anybody have an idea of what the problem might be?