Antitheft and Alarm Systems: Description and Operation

ANTI-THEFT

The passive anti-theft system (PATS) uses radio frequency identification technology to deter a driveway theft. Passive means that it does not require any action from the user to make it functional.

PATS uses a specially encoded ignition key. Each PATS key contains a permanently installed electronic device called a transponder. Each transponder contains a unique electronic identification code, with over 72 million billion combinations.

Each PATS key must be programmed into the vehicle PATS module before it can be used to start the engine. There are special diagnostic procedures described in the that must be carried out if new PATS keys are to be installed.

The PATS key is larger than a traditional ignition key. The PATS key does not require batteries and should last the life of the vehicle.

The PATS transceiver is located on the steering column attached to the ignition lock cylinder housing and communicates with the PATS keys. During each vehicle start sequence, the PATS transceiver reads the PATS key identification code and sends the data to the instrument cluster. The instrument cluster validates the code as correct and sends the powertrain control module (PCM) an enable code through the network.

The control function is contained in the instrument cluster. The instrument cluster carries out all of the PATS functions, such as receiving the identification code from the PATS key and controlling the starter enable signal, and communicates with the PCM to enable the engine. The instrument cluster initiates the key interrogation sequence when the PATS key is inserted in the ignition switch and also when the switch is turned to RUN or START.

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

NOTE: If either the instrument cluster or the PCM are installed, both modules require a parameter reset to allow the modules to recognize the PATS keys. Failure to carry out the parameter reset to both the instrument cluster and PCM may result in a no-start condition.

The PATS uses a visual anti-theft indicator (part of the light sensor). This indicator proves out for 3 seconds when the ignition switch is turned to ON or START. If there is a PATS concern, this anti-theft indicator either flashes rapidly or glows steadily (for more than 3 seconds) when the ignition switch is in the RUN or START position. The PATS also flashes the anti-theft indicator every 2 seconds with the ignition switch OFF to act as a visual theft deterent.

The PATS is not compatible with aftermarket remote start systems, which allow the vehicle to be started from outside the vehicle. These systems may reduce the vehicle security level and may also cause no-start issues. Remote start systems must be removed before investigation of PATS-related no-start issues.