Hi, I am building a DIY rpm gauge and I plan on using the trigger on the coil pack as a rpm signal. As far as I know its negatively triggered so I thought you would have one wire 12v and the other wire pulses GND from the ecu. Using a multimeter I have tested both wires off the first coil pack and both seem to be a GND wire with the ignition turned on. Maybe it all changes when the engine is running. Theres a yellow/black wire and a white/orange wire. If someone could shed some light on the situation it would be appreciated thanks.