First, check the switch header on your board. That is two pins. with your multimeter, set it to 12 volts DC range. Take one probe and connect it to ground somehow. Take the other probe, and touch it to the first pin, and then the second pin. See if it shows 12 volts?
ALSO, with the cable disconnect between J8 and the MB, put your multimeter into "continuity" mode, and connect one probe to the red wire, and the other probe to the black wire. Then, simulate the ignition wire (you can turn the key if you want, whatever you can to simulate the ignition) and then see if there is continuity all the time, never, or briefly.
Then, report back.