I was not suggesting that you would find a dangling ground wire. In the little wiring harness that is part of the GI Pro, there should be three conductors (wires). Red, green and black. In your picture, I see the green (ground) wire. The three wires are for power, signal and ground. In my case, I kept getting C31 code. Failed gear position sensor. I struggled with this problem for a long time. I replaced the gear position sensor and the GI Pro. By the way, the problem was intermittent, which made it more difficult to diagnose. Finally, one of the guys at Healtech suggested that I get the ground wire in the GI Pro harness connected directly to the battery. I taped into the green wire, connected it to the negative terminal of the battery and all has been good.
Send a note to support at Healtech and they will help you with connecting the ground wire to the battery.