A real puzzler....electric step issue

Ok, on my 2007 Journey, the electric step started to malfunction. It goes in and out with the door opening and closing as it is supposed to. However, if you have the switch in the "stay out" position, it stays out all the time. When you turn the ignition on, it does not retract like it is supposed to.

The manual for the step states that the yellow wire in the four wire connector should have 12 volts on it when the ignition is turned on. I disconnected it and measured the voltage at 2 volts. Not good. Well, about 6 inches further up the wires is another, identical 4 wire plug. I pull that one and the yellow wire has 12 volts!

Now here is the puzzling part, in the wiring between the two connectors a green wire is spiced into the yellow wire. The green wire goes to a ground bolt. Between the yellow wire and ground there is a resistance of 1.8 Kohms. So it is obviously not a direct connection, but almost like there is a resistor or maybe a diode in the splice. The owners manual does not say anything about this wire. I removed this intermediary piece and connected the two 4 wired connectors together directly, eliminating the green wire. The step functions perfectly.

Below are two pictures of the extension piece, and then one of the plugs with the extension removed.

So what is the function of the green wire?

thanks, jeff