I seen that.. I thought that someone on here may have a trick or something i haven't heard or thought of.. I was thinking maybe instead of useing the the parking brake maybe they used the transmission or a speed sensor? I would try the ground wire but it only plays while the truck is in park with the break on or off..It's a little more complicated than that with an OE system, it obtains the info through the vehicle's CAN bus data. The system knows everything, if it's in park, if the park brake is on, and if the vehicle is in motion and what speed. It is not a simple work around like an aftermarket unit, you need to manipulate the vechile data at the BCM