Abstract: An unattended-vehicle engine-idling system controls a vehicle powertrain in a non-motive mode with the engine running. An ignition switch operables with a removable ignition key. A control circuit has multiple states including a PREARMED state which is entered when the powertrain is in the motive mode and the user generates a manual activation signal. An ARMED state is entered when the transmission is in Park and holds an ignition switch status signal at RUN. An ACTIVE state is entered when the ignition switch is moved to the Accessory or Off positions or the key is removed. The powertrain is switched to non-motive mode and the switch status signal stays at RUN. A DISARMED state is entered in response to a manual deactivation signal generated independently of the ignition switch. In the DISARMED state, the ignition switch status signal corresponds with the ignition switch position, thereby turning off the engine.