Vehicle Theft Deterrent (VTD) Description
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 Theft Deterrent Controller Module - which must receive the unique key value and then sends a unique password
The PCM - which must receive the correct password from the theft deterrent controller module to enable engine starting

The Ignition Key (Transponder)
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 in order 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:

Start the vehicle.
Lock/unlock all of the door locks.
Lock/unlock all of the storage compartments.
Lock/unlock the rear compartment lid lock.
Lock/unlock the rear compartment valet lock out switch, which is located on the IP.

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

The valet key may perform the following functions:

Start the vehicle.
Lock/unlock all of the door locks.
The valet key cannot perform the following functions:

Lock/unlock all of the storage compartments.
Lock/unlock the rear compartment lid lock.
Lock/unlock the rear compartment valet lock out switch, which is located on the IP.

Ignition Lock Cylinder
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 .

Theft Deterrent Controller Module and Exciter
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. The theft deterrent controller module 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, the module sends an enable password to the PCM via the class 2 serial data line. If the transponder value is not correct, the module sends a disable password to the PCM.

Powertrain Control Module (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:

The enable password incorrect.
The system disable password is sent by the theft deterrent controller module.
No passwords are received - no communication occurs with the theft deterrent controller module.

Vehicle Theft Deterrent (VTD) Operation
When an ignition key is inserted into the ignition lock cylinder, the transponder embedded in the head of the key is energized by the exciter coils surrounding the ignition lock cylinder. The energized transponder transmits a signal that contains its unique value, which is received by the VTD Controller Module . The VTD Controller Module then compares this value to a value stored in memory and performs one of the following functions:

If the transponder value is correct, the VTD Controller Module sends a class 2 message containing the module's unique enable password to the PCM.
If the transponder value is incorrect, the VTD Controller Module sends a class 2 message containing a disable password to the PCM.
If the VTD Controller Module is unable to measure the ignition key transponder value for one second, due to a damaged or missing pellet or a damaged exciter, the VTD sends a class 2 message containing a disable password to the PCM

Important
If the VTD Controller Module is unable to measure the ignition key transponder value for 30 consecutive seconds, after the vehicle has started, the module will consider itself malfunctioning and enter a fail enable state and illuminate the Security Indicator. The vehicle will not stall or stop running. If the VTD Controller Module is in a fail enable state when the ignition is turned to OFF, it will remain fail enabled until the next time the vehicle is started. If the VTD Controller Module is fail enabled the Pass Key® III system is NOT active and the vehicle will start. The module WILL send its enable password even if a transponder value is not received. The VTD Controller Module will remain fail enabled until the module measures a valid key transponder value.


When the PCM receives a password from the VTD Controller Module, the PCM compares the password to a password stored in its memory (learned password) and performs one of the following functions:

If the PCM receives a correct system enable password, indicating a learned VTD Controller Module has a read a valid transponder value, fuel and starting are enabled.
If the PCM receives a system disable password, indicating a VTD Controller Module has a read an invalid transponder value, fuel and starting are disabled.
If the PCM receives an incorrect password, indicating a VTD Controller Module that has not been learned by the PCM, fuel and starting are disabled.
If the PCM has no communication with the VTD Controller Module, fuel and starting are disabled.

Important
If the PCM is unable to communicate with the VTD Controller Module (loss of class 2 state of health) after the vehicle has started, the module will consider itself malfunctioning and enter a fail enable state and illuminate the Security Indicator. The vehicle will not stall or stop running. If the PCM is in a fail enable state when the ignition is turned to OFF, it will remain fail enabled until the next time the vehicle is started. If the PCM is fail enabled the Pass Key® III system is NOT active and the vehicle will start. The PCM will remain fail enabled until class 2 communication with the VTD Controller Module is restored.


SECURITY Indicator Operation
The VTD Controller Module can command the instrument cluster to illuminate the SECURITY indicator only when the ignition key is in the ON position. If the PCM loses communication with the VTD Controller Module, the instrument cluster will also detect the loss of communication and will illuminate the SECURITY indicator. The SECURITY indicator can indicate both malfunctions - the indicator on steady, and tamper - the indicator flashes indicating unauthorized operation. Under the following conditions the SECURITY indicator may be commanded to illuminate.

SECURITY Indicator Stays Illuminated and Engine Starts
If the VTD Controller Module was unable to measure the ignition key transponder value or the PCM lost communication with the VTD Controller Module while the engine was last running, the indicator will remain illuminated during subsequent ignition cycles. This is to remind the driver that the vehicle theft deterrent system will not be functioning until the problem is corrected. The vehicle is fail enabled and will start.

SECURITY Indicator Illuminates when Engine is Running
If the VTD Controller Module is unable to measure the ignition key transponder value or the PCM loses communication with the VTD Controller Module while the engine is running, the indicator will be illuminated. If the key is turned to OFF, the vehicle will be fail enabled and will start if the condition still exists at the next attempt to start the vehicle.

SECURITY Indicator Illuminated and Engine Does Not Start
The VTD Controller Module or the PCM has detected a problem with the PASS-Key® III system. The VTD Controller Module is unable to measure the ignition key transponder value. The System is in Learn Mode, refer to Programming Theft Deterrent System Components .

SECURITY Indicator Flashes and Engine Does Not Start
The VTD Controller Module has measured an incorrect transponder value when the ignition key is turned to the ON position. The transponder has not been learned by the VTD Controller Module. This is considered a tamper condition by the Module.

SECURITY LED
The VTD controller Module commands the instrument cluster to illuminate the theft LED located in the interior dimming switch. The instrument cluster receives a class II message from the VTD controller module to control this LED. It is intended to be used as another theft deterrent and indicate that the VTD system is in the ARMED state of readiness.