How to Reset the Passlock System on a 2000 Silverado. The 2000 Chevrolet Silverado featured GM's Passlock II security system, designed to disable the engine if the body control module fails to receive an expected signal from the ignition key lock cylinder. The required “signal” is actually a specific analog resistance value, learned and stored in the BCM. Damage to the BCM, the sensor -- located inside the ignition lock cylinder -- or the wiring may activate the system, causing a no-start condition. After you replace the cylinder or BCM, or as a temporary measure to start the vehicle due to a failing sensor, you'll have to reset the Passlock system.
Insert the key into the ignition and crank the engine for two to three seconds. Leave the key switched to the “ON” position until the “SECURITY” lamp stops flashing position, approximately 10 minutes. Switch the ignition to the “OFF” position for five seconds.
Repeat Step 1 two more times to complete the reset procedure.
Turn the ignition switch to the "OFF" position and start the engine. Repeat the reset process again if the first attempt was unsuccessful.