Principles of Operation

PRINCIPLES OF OPERATION

The passive anti-theft system (PATS) uses a specially encoded ignition key. Each PATS key contains a permanently installed electronic device called a transponder. Each transponder contains a unique encrypted identification code out of over 18 billion combinations.

Each PATS key must be programmed into the powertrain control module (PCM) before it can be used to start the engine. There are special diagnostic repair procedures that must be carried out if a new PATS key is necessary.

This system contains a new feature named Unlimited Key Mode. This feature allows a customer to program more than eight keys to their vehicle if they request it. Each vehicle in Unlimited Key Mode is set up with a special Unlimited Transponder Security Key. This allows all the customer vehicles to share the same keys, but no other keys from outside can be used to operate the vehicles. For an individual customer, any randomly selected security key is acceptable. Refer to Key Programming - Unlimited Key Mode.

The PATS transceiver module energizes the transponder in the PATS key. The module is located behind the steering wheel column shroud and contains an antenna connected to a small electronics module.

The control functions are contained in the PCM. This module carries out all of the PATS functions, such as receiving the identification code from the PATS key and controlling the engine enable. The PCM initiates the key interrogation sequence when the vehicle ignition switch is turned to RUN or START.

All elements of the PATS must be functional before the engine is allowed to start. If any of the components are not working correctly, the vehicle will not start.

The PATS uses a visual theft indicator located in the instrument cluster. The indicator will prove out for 3 seconds when the ignition switch is turned to RUN or START under normal operation. If there is a PATS problem, this indicator will either flash rapidly or glow steadily when the ignition switch is turned to RUN or START. The PATS system also flashes the theft indicator every two seconds at ignition OFF to act as a visual deterrent.

The PATS will be activated and will disable the vehicle from starting if there is:
- incorrectly encoded PATS key.
- damaged PATS key.
- unprogrammed key.
- non-encoded key (key has no electronics).
- damaged wiring.
- damaged transceiver.
- damaged PCM.