Am planning to install a carputer (Raspberry Pi) in a 2005 Ford Mondeo, replacing the car stereo. The Quadlock connector to the stereo apparently includes CAN bus, so I am thinking I will get a USB OBD-II adapter and just solder the relevant pins.
6, 14, 16 are CAN bus and battery plus.
On 4 it says "chassis ground" and on 5 "signal ground". I think I understand linguistically what that means, but am not sure why you need both. (Is that even the CAN bus signal?)
Since I only have one "ground" on the Quadlock, which I assume is battery minus, connected to the chassis, what should I do?
Both 4 & 5 to ground or ignore OBD-II pin 5?
Clarification: I am not going to use the car OBD-II port, only the Quadlock connector.
Edit: what I am really wondering is why the OBD-II standard has both chassis and signal ground. I find it hard to believe they are just the same.
More clarification: the car has an OBD-II port under the steering wheel. I am not talking about that one. The one I mean is the "in" connector to an adapter for interpreting the bus computationally. The adapter is connected to the computer via USB. I am going to remove that connector and connect the pins I need to the car via the Quadlock connector.