Passlock™ System

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The theft deterrent system has been incorporated into the body control module (BCM). The theft deterrent is provided in order to prevent the vehicle operation if the correct key is not used in order to start the vehicle. The ignition key turns the lock cylinder. The cylinder rotation produces an analog voltage code in the Passlock™ sensor. This voltage code is received by the BCM. The BCM compares the voltage code to the previously learned voltage code. If the codes match, a class 2 message is sent from the BCM to the powertrain control module (PCM)/vehicle control module (VCM). The message enables the fuel injectors.

The design of the Passlock™ system is to prevent vehicle theft by disabling the engine unless the ignition lock cylinder rotates properly by engaging the correct ignition key. The system is similar in concept to the PASS-Key® system. However, the Passlock™ system eliminates the need for a key mounted resistor pellet. The components of the Passlock™ system are as follows:

The ignition lock cylinder
The ignition switch
The Passlock™ sensor
The Body control module (BCM)
The security telltale
The vehicle/powertrain control module (VCM/PCM)