IMMOBILIZER SYSTEM (PATS) OPERATION


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The immobilizer system uses radio frequency identification technology to deter a drive away theft.
The immobilizer system uses a specially encoded ignition key. Each encoded ignition key contains a permanently installed electronic device called a transponder. Each transponder contains a unique electronic identification code of over four quadrillion possible combinations.
Each encoded ignition key must be programmed into the vehicle’s powertrain control module (PCM) before it can be used to start the engine. There are special diagnostic repair procedures described in this section that must be performed if a new encoded ignition key is necessary.
The coil antenna communicates with the encoded ignition key. The coil antenna is located behind the steering wheel column and contains a coil antenna connected to a compact electronic module. During each vehicle start sequence, the coil antenna reads the encoded ignition key identification code and sends data to the PCM.
The control functions are contained in the PCM. This module performs all of the immobilizer functions, such as receiving the identification code from the encoded ignition key and controlling the engine start/off. The PCM initiates the key interrogation sequence when the ignition switch is turned to the ON or START position.
All elements of the immobilizer system must be functional before the engine can be started. If any of the components are not working correctly, the engine will not start.
The immobilizer system uses a visual security light. The security light will prove out for three seconds when the ignition switch is turned to the ON or START position under normal operation. If there is an immobilizer system malfunction, the security light will either flash rapidly or glow steadily when the ignition switch is turned to the ON or START position. The immobilizer system also flashes the security light every two seconds when the ignition is turned off to act as a visual theft deterrent. The security light is located in the instrument cluster. The security light is controlled through the standard corporate protocol (SCP) communication network. The PCM sends the security light signal through the SCP communications network to the instrument cluster. The instrument cluster then triggers the security light to illuminate.
The immobilizer system will be activated and will disable the vehicle from starting if any of the following occur:
•  An incorrectly coded ignition key.
•  A damaged encoded ignition key.
•  An unprogrammed key.
•  A non-encoded key (key has no electronics).
•  Damaged wiring harness.
•  A damaged coil antenna.
•  A damaged PCM.
•  A module communications network malfunction.