Abstract: An anti-theft sensor contact mechanism for an ignition system of an automotive vehicle has a sensor contact mechanism 24 which utilizes a non-conducting lever 46 to sense the physical presence of a lock liner 26 within a lock cylinder 28 of the ignition system and to depress a moveable contact 40 against a stationary contact 38 of the same metal for closing a path in an electrical monitoring, or sensing, circuit 32. When the lock liner 26 is removed, such as when tampered with during theft of the vehicle, the sensor contact mechanism 24 causes a break in an electrical path in the circuit 32 through movement of the moveable contact 40 to a non-contacting position with the stationary contact 38 so that a conventional alarm system may be triggered to sound an audible or visible.