For 1990-2009 cars

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 PCM will remain fail enabled until class 2 communication with the theft deterrent controller module is restored.

### SECURITY Indicator Operation

The theft deterrent 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 theft deterrent 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-indicator on steady, and tamper-indicator flashing, indicating unauthorized operation. Under the following conditions the SECURITY indicator may be commanded to illuminate.

#### SECURITY Indicator Stays Illuminated and Engine Starts

If the theft deterrent controller module was unable to measure the ignition key transponder value or the PCM lost communication with the theft deterrent 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 theft deterrent controller module is unable to measure the ignition key transponder value or the PCM loses communication with the theft deterrent 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 theft deterrent controller module or the PCM has detected a problem with the theft deterrent system. The theft deterrent 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 theft deterrent 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 theft deterrent controller module. This is considered a tamper condition by the module.