2008 f-150 5.4L/ tuner will not turn on through OBD cord

[Mattj5456]

I plugged in my tuner and it got no power. So I checked the female end of the plug to make sure everything was wired okay and it all checked out. Then I tried plugging in the sub cord with the obd2 cable and it powered up and gave me readings through the tuner (battery voltage, rpm's etc). When I clicked on the performance to try and tune it gives me an error message that says low voltage please charge battery. I checked my voltage and the battery is at 13v. I'm confused as to why it isn't powering up just through the OBD2 cable but it is giving me a reading when plugged in with a sub cord?? Can anyone help?

[mikel]

blown cig lighter fuse in the truck?