Where are you getting this reading? I spliced my positive at the left back-up light in the tail gate. Never checked the voltage.

I took care to run the ground out of the gate to where other grounds connected inside the spare area.

Maybe you need to run that test again using a better ground or check it against the battery in the X and also in another car.

Was your battery low because you were screwing around with wiring and stuff and had the gate open for a long time? I have heard this can happen...