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 the correct key is used to start vehicle, a magnet on lock cylinder passes close to Passlock(tm) sensor within ignition lock cylinder case. The 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.

When DTC P3031 sets, vehicle will not run. The security indicator will remain illuminated. DTC B3031 will clear after an ignition cycle has occurred after the BCM has learned a valid code.