I'm getting 5.66V or so on both of them, so maybe I don't have the right connections.

I can't find a good reference for the pinouts on the 2012 Charger since it's a relatively new vehicle, but the physical shape of the plug and the number of pins matches this guy, and this PDF does list the pinouts, with pin 2 labeled "CAN BUS (+)" (which I've connected to the CAN-H input) and pin 13 labeled "CAN BUS (-)" (connected to CAN-L.)