General Description

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 theft deterrent controller module.

The theft deterrent 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 theft deterrent controller module sends a class 2 message containing the module's unique enable password to the PCM.
^ If the transponder value is incorrect, the theft deterrent controller module sends a class 2 message containing a disable password to the PCM.
^ If the theft deterrent 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), it sends a class 2 message containing a disable password to the PCM

IMPORTANT: If the theft deterrent 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 theft deterrent 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 theft deterrent controller module is "fail enabled" the theft deterrent 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 theft deterrent controller module will remain "fail enabled" until it measures a valid key transponder value.

When the PCM receives a password from the theft deterrent 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 theft deterrent controller module has read a valid transponder value, fuel and starting are enabled.
^ If the PCM receives a system disable password, indicating a theft deterrent controller module has read an invalid transponder value, fuel and starting are disabled.
^ If the PCM receives an incorrect password, indicating a theft deterrent controller module that has not been learned by the PCM, fuel and starting are disabled.
^ If the PCM has no communication with the theft deterrent controller module, fuel and starting are disabled.

IMPORTANT: If the PCM is unable to communicate with the theft deterrent 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 theft deterrent system is NOT active and the vehicle will start. The PGM will remain "fail enabled" until class 2 communication with the theft deterrent controller module is restored.