How does the Passlock System work on the Oldsmobile Achieva?

The Passlock System on the Oldsmobile Achieva is a passive anti-theft feature that disables the engine if an unauthorized key is used. It relies on a sensor in the ignition lock cylinder that detects the presence of a specially coded key. When the key is turned, the sensor sends a signal to the engine control module (ECM); if the signal matches the stored code, the ECM allows the engine to start. If the code does not match, the system activates the fuel cutoff, preventing the engine from running.