Quick question, I have 2 vehicle speed sensors on the side of my 4l80e trans but only the front is plugged in. I've done some reading and it looks like the 4wd trucks may use a (third?) speed sensor in the transfer case. I don't see a loose pig tail for the rear transmission sensor, is it just serving as a plug? The reason I'm asking is that I'm getting a 72 DTC and wonder if it's a bad sensor or if it's because I have a sensor that's not plugged in.

Thanks