Antitheft and Alarm Systems: Description and Operation

PASSLOCK(TM) THEFT DETERRENT
The PASSLOCK theft deterrent system is designed to prevent vehicle theft by disabling the engine's fuel system and starter motor unless the ignition lock cylinder is rotated by using the proper ignition key. The PASSLOCK theft deterrent system is similar to the PASS-Key II theft deterrent system. However, the PASSLOCK theft deterrent system eliminates the need for a resistor pellet embedded in the ignition key.

The PASSLOCK is a vehicle theft deterrent system. The PASSLOCK theft deterrent system contains a PASSLOCK sensor. The PASSLOCK sensor is part of the ignition lock cylinder assembly. The body control module (BCM) provides power and ground to the PASSLOCK sensor. The PASSLOCK sensor interfaces with the BCM through the PASSLOCK detection circuit 1836.

When turning the ignition switch to the start position with the proper key, the PASSLOCK sensor generates an analog voltage signal. This signal is sent through the PASSLOCK detecting circuit. This analog voltage signal is of a specific value to the vehicle, and varies from vehicle to vehicle. When attempting to start the engine, the BCM compares a preset stored analog voltage value with the signal coming from the sensor. Because both values match, the BCM sends a fuel enable password via the Class 2 serial data link to the powertrain control module (PCM). As a result, the PCM enables the crank relay, and allows fuel delivery to the engine.

When attempting to start the engine by means other than using the proper key in the ignition switch, the PASSLOCK sensor sends a analog voltage signal of a different value. The BCM compares the preset stored analog voltage value with the signal coming from the PASSLOCK sensor. Because both values do not match, the BCM sends a fuel disable password via the Class 2 serial data link to the powertrain control module (PCM). As a result, the PCM disables the crank relay, and does not allow fuel delivery to the engine.

Refer to Body Control System Operation in Body Control Module for more information regarding the BCM.

BCM INPUTS
The following components provide direct input to the BCM, plus other systems can use this input information in order to carry out PASSLOCK theft deterrent functions:
^ BCM Ground: Provides ground for BCM operation.
^ BCM Power: Provides voltage for BCM operation.
^ Crank Signal: Determines when the ignition switch is in the start position.
^ Ignition 0 Signal: Determines when the ignition switch is in accessory, on, and start positions.
^ Ignition 1 Signal: Determines when the ignition switch is in the on, bulb test, and start positions.
^ Passlock(TM) Sensor Data: Reads the PASSLOCK sensor security code.
^ Serial Data: Provides an interface with the PCM through the Class 2 serial data link.

BCM OUTPUTS
The BCM directly controls these outputs for PASSLOCK theft deterrent functions:
^ Passlock(TM) Sensor Power: Provides B+ for PASSLOCK sensor operation.
^ Passlock(TM) Sensor Ground: Provides ground to the PASSLOCK sensor.
^ Serial Data: Provides an interface with the PCM and the instrument cluster through the Class 2 serial data link.

THEFT DETERRENT RE-LEARN
Perform the Theft Deterrent Re-Learn procedure when:
^ The BCM has been replaced in the vehicle and the Setup New BCM procedure has been successfully completed.
^ The ignition key cylinder assembly has been replaced.

Refer to BCM Programming/RPO Configuration in Body Control System for the Theft Deterrent Re-Learn and the Setup New BCM service procedures.