Principles of Operation

PASSIVE ANTI-THEFT SYSTEM (PATS) - PRINCIPLES OF OPERATION

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

The 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 transceiver before it can be used to start the engine. There are special diagnostic procedures that must be carried out if new PATS keys are to be installed. Refer to general procedures.

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 module communicates with the PATS key. This transceiver is located in the instrument panel attached to the ignition cylinder housing. 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 when the ignition switch is turned to RUN or START.

The PATS transceiver uses the instrument cluster to enable or disable the engine. 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 will not start.

NOTE: If either the instrument cluster or the PCM is installed, each requires a parameter reset to allow it to recognize the PATS keys. Failure to carry out the parameter reset to the instrument cluster or the PCM may result in a no-start condition.

The PATS uses a visual theft indicator. This indicator proves 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 either flashes rapidly or glows steadily, for more than 3 seconds, when the ignition switch is turned to RUN or START.

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 also may cause no-start issues. Remote start systems must be removed before investigation of PATS-related no-start issues.