Circuit Description

WARNING: This page is about a different car, the 2002 GMC Savana, 2002 Chevrolet Chevy Express, 2001 GMC Savana, and 2001 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.

Passlock(tm) system is provided in order to prevent vehicle theft if the ignition lock cylinder is forced to rotate or ignition switch is operated while separated from ignition lock cylinder case. Passlock(tm) module provides security system sensor power and low reference for Passlock(tm) sensor. Passlock(tm) module also measures security system sensor voltage. When correct key is used to start vehicle, a magnet on lock cylinder passes close to Passlock(tm) sensor within ignition lock cylinder case. Magnet activates the security Hall Effect sensor in the Passlock(tm) sensor which completes a circuit from security sensor signal circuit through a resistor to security sensor low reference circuit. Resistance value will vary from vehicle to vehicle. Passlock(tm) module will measure voltage on security sensor signal circuit and compare this voltage to a previously learned voltage. If voltage measured is within the valid range, Passlock(tm) module will send a class 2 message to Powertrain Control Module (PCM) to enable vehicle starting. If voltage measured is not within the valid range, a class 2 message will be sent to PCM to disable starting of vehicle.

Vehicle will not start if fault occurs before starting vehicle. SECURITY indicator will illuminate. If vehicle is running when fault occurs, Passlock will be in fail enable mode allowing vehicle to start and to run. SECURITY indicator will be illuminated. DTC will clear after an ignition cycle occurs without fault recurring. Passlock(tm) history code clears after 100 concurrent ignition cycles occur without the fault recurring. DTC can also be cleared using a scan tool.