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 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 security Hall Effect sensor in 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 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 valid range, a class 2 message will be sent to PCM to disable starting of vehicle.

DTC will set only when engine is running. Passlock(tm) module will be in fail enable mode allowing vehicle to start and run. SECURITY indicator will be illuminated. Current DTC will clear once an ignition cycle has occurred without fault recurring. A history DTC clears after 100 concurrent ignition cycles occur without fault recurring. DTCs can be cleared using a scan tool.