Anti-Theft Systems: Description

WARNING: Vehicles are equipped with air bag supplemental restraint system. Before attempting ANY repairs involving steering column, instrument panel or related components, see SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM in appropriate AIR BAG RESTRAINT SYSTEMS article.

The passlock system is a vehicle theft deterrent system which deters drive-away vehicle theft by disabling engine operation if the ignition lock cylinder is not rotated with the proper mechanically cut key.

The passlock system is made up of an ignition switch assembly, passlock sensor, body control module (BCM), instrument panel cluster (IPC), and a powertrain control module (PCM).

The ignition switch contains a magnet mounted on the lock cylinder and a passlock sensor assembly which consists of security hall effect sensor, tamper hall effect sensor, and output resistors. A drill proof metal shield is also staked over the sensor housing.

The passlock sensor mounted to the ignition switch assembly is located inside the upper right side of the steering column. The passlock sensor contains two hall effect sensors: a tamper hall effect sensor and a security hall effect sensor. The tamper hall effect sensor is mounted on top of the security hall effect sensor. Should someone attempt to defeat the system by use of magnetic experimentation, the tamper hall effect sensor will activate first.

The BCM has the passlock controller integrated into it which controls the majority of the security systems logic. The BCM reads the data from the passlock sensor continuously. If the data is correct and has been received by the BCM within a specified time, the BCM will send a coded password to the PCM. The PCM will then allow the fuel injectors to operate.

The coded password for the security system is sent from the body control module to the PCM via the class 2 data link. If the password is correct and received within the specified time, the PCM will allow the fuel injectors to operate.

The IPC contains the security telltale. The security telltale has three modes of operation, OFF, FLASHING, and ON.

SECURITY TELLTALE will be off if:

Ignition is in the OFF position
Ignition is in the RUN, START, or ACC position and security system diagnostics have all PASSED

SECURITY TELLTALE will be ON if:

The BCM is performing a bulb check at vehicle start
Security system diagnostics have not yet completed at vehicle start
A security system diagnostic trouble code (DTC) is set in the BCM or PCM

SECURITY TELLTALE will be flashing if:

The tamper hall effect sensor has been triggered
Incorrect passlock sensor data to BCM for more than 5 seconds during vehicle start
No passlock sensor data to the BCM for more than 5 seconds during vehicle start
Incorrect password from the BCM to the PCM after 5 seconds during vehicle start