Shut down on Idle Mode

Question

As I'm working on an installation that's still giving me problems, I have a new question which may solve my others problems. Using an evo-one, programmed and setup as tachless, upon trying to use Idle Mode, the car turns off after about 5 seconds after turning the ignition off and I get 4 flashes meaning no tach signal. What could cause this during Idle Mode?