I had a similar thing with my 07 Journey. In the wiring goi g to the step, there was a short "extension cord" connected to the plug coming from the chassis and then to the plug goi g to the steps. In the short extension there was a wire coming out going to ground. It turns out that extension has a diode in it protecting the the step circuit board from an over voltage. The diode had shorted the wire to ground. I removed the etension and plugged the step connector directly into the chassis connector, and the step worked perfectly. This was an easy workaround until I replaced the diode.
Don't know if that helps you......good luck.
Jeff