I have a s15 with 1and half jz installed i have a ignition switch inside car that will start and cut the engine 100% … but it needs a emergency out side main cut off switch..if the car is idling and you turn off the main switch it does not cut off the engine the main switch is wired -terminal
the main kill switch is not installed correctly, and is feeding power from the alternator to keep the ecu active. check your wiring and make sure power is removed from the ECU, and it will be all good. You can also cut power to the fuel pump, to remove fuel from the system.