FG Barra into Patrol - Start Circuit cheat / bypass

Hey Guys, Im chasing some specifics on how to wire up a simulated push button start into the FG harness. Would prefer not to actually wire up the starter to a push button - just simulate what ever we need at ECU to keep it happy.

The FG ECU needs to think the push button is starting the engine otherwise it shuts the motor down after 2 seconds - like an immobiliser. There is a hack to select the auto trans in the tune and the motor starts and runs but causes side effects because it now thinks its an auto - so we need to wire in some type of simple simulation - hoping someone has done it and kept some notes!?
S1 FG Manual 2008.