The vehicle theft deterrent (VTD) functions are provided by the Passlock system. Passlock consists of the following components:
| • | A standard ignition key |
| • | An ignition lock cylinder assembly, including a Passlock sensor |
| • | The body control module (BCM) |
| • | The powertrain control module (PCM). |
The Passlock sensor contains a magnet on the lock cylinder and a hall effect switch on the surrounding assembly. When you rotate this cylinder using an ignition key with the proper mechanical cut, the magnet on the lock cylinder activates the hall effect switch. When activated, the Passlock sensor provides a unique resistance value to the Passlock data circuit of the BCM. The resulting voltage is measured by the BCM. This voltage value is compared to one stored in memory (a learned value). If the Passlock data voltage value matches the learned value, the BCM sends a password, via the class 2 serial data link, to the PCM. The PCM compares this value to one stored in memory (a learned password). If the passwords match, the PCM enables engine starting.
The following functions, therefore, provide vehicle theft deterrence:
| • | The password, which is unique for each BCM |
| • | The many resistance possibilities for the Passlock ignition lock cylinder assembly |
| • | The mechanical key cut possibilities for the ignition keys |
In addition, any attempt to forcibly remove the ignition lock cylinder will destroy the Passlock sensor. If anyone tries to fool the Passlock sensor with an external magnet, a "tamper" hall effect switch will be engaged and an invalid "tamper" resistance value will be provided to the Passlock Data Circuit from the BCM.
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.
