The vehicle VTD functions are provided by the Pass Key® III system. Pass Key® III consists of an ignition key with a transponder embedded in the head, the theft deterrent controller module, the exciter assembly, and the PCM.

The exciter assembly is an antenna which is made up of wire coils which surround the ignition lock cylinder. These coils, powered by the theft deterrent controller module, emit electromagnetic energy which energizes the transponder pellet within the head of the key. The energized transponder transmits a unique value by radio frequency which is detected by the exciter. The theft deterrent controller module receives and compares this value to one stored in memory (a learned value). If the received transponder value matches a learned value, the theft deterrent controller module sends a password via the class 2 serial data line to the PCM. The PCM compares this password to one stored in memory (a learned password). If the passwords match the PCM enables engine starting.

This password is unique for each theft deterrent controller module along with the unique value of the key's transponder. This method prevents swapping one of the following modules in order to start the vehicle:

The ignition key for theft deterrent equipped vehicles is a typical looking ignition key with a transponder located in the plastic end of the key. The transponder value is fixed and unable to be changed. The theft deterrent system uses the ignition key transponder value to determine if a valid ignition key is being used to start the vehicle. There are approximately 3 trillion possible transponder values. There are no visible electrical contacts. The keys may be identified by the letters "PK3" stamped into the steel shank of the key. The theft deterrent systems use the following types of ignition keys:

Master Keys

Master keys (black plastic end) are for full access operation of the vehicle. Master keys may perform the following functions

Valet Keys

Valet keys (gray plastic end) are for restricted operation of the vehicle

The ignition lock cylinder performs all of the functions of a lock cylinder on a non theft deterrent equipped vehicle. The ignition lock cylinder for vehicles with theft deterrent may be located on the steering column or on the instrument panel. In either location the exciter coils surround the ignition lock cylinder such that they are very close to the head of the key which contains the transponder pellet.

If an ignition lock cylinder is replaced, new transponder keys must be cut to match the mechanical coding of the new lock cylinder. The new keys must be learned by the theft deterrent controller module. When replacing an ignition lock cylinder, refer to Programming Theft Deterrent System Components

Vehicles with steering column mounted ignition switches have the exciter integral with the theft deterrent controller module which is located within the steering column. Vehicles with instrument panel mounted ignition switches have exciter modules separate from the theft deterrent controller module with the vehicle wiring harness connecting the two. The theft deterrent controller module for vehicles with instrument panel mounted ignition switches is located within the instrument panel.

The theft deterrent controller module can learn up to ten keys (transponder values).

The theft deterrent controller module provides the signal to the exciter which energizes the transponder within the key. It also receives and verifies the transponder signal value. When the theft deterrent controller module has verified that the transponder signal value matches the value of a learned key, it sends an enable password to the PCM via the class 2 serial data line. If the transponder value is not correct, it sends a disable password to the PCM.

The PCM verifies that the password received from the theft deterrent controller module via the Class 2 serial data line is correct. The theft deterrent controller module can learn only one enable password. If the enable password is correct, the PCM enables the fuel system and engine starting system.

The PCM disables the fuel and starting systems if any of the following conditions occur: