When the alarm is armed, the interior motion sensor detects movement within the vehicle's interior, including air movement through open apertures.
When the alarm is fully armed and the interior motion sensor is active, any significant movement within the passenger compartment activates the alarm.
The interior motion sensor is a sensor for the alarm system. Various alarm sensors can be enabled and disabled, for one ignition cycle only, via the Vehicle menu in the touchscreen. See SYSTEM SETTINGS.