Antitheft and Alarm Systems: Description and Operation

The Passive Anti-Theft System (PATS) uses radio frequency indentification technology to deter a driveaway theft.Passive means that it does not require any activity from the use.
^ During each vehicle start sequence, the ignition key identification code is requested by the PATS module.
^ If the key's ID code has been programmed into the system, the vehicle Powertrain Control Module (PCM) is allowed to operate;this allows the vehicle to start.
^ If the key's ID code is programmed into the PATS module, or if no encoded key is detected, then the vehicle PCM is disabled.

The PATS module, located under the driver side instrument panel, communicates the state of the security system to the PCM via the module communication network. The PCM, based on the communications from the PATS module, will determine if the vehicle's engine will be enables to start. If the PCM prevents the vehicle from starting because of PATS, the PCM will stare a DTC in memory.

The anti-theft vehicle protection system utilizes the THEFT indicator, located in the instrument cluster, when the ignition switch is turned to the RUN/START position. The indicator provides system prove out and operating status to the customer or technician.

Each PATS ignition key holds electronics that give each key a unique ID code.

The PATS will activate the indicator signal when the ignition switch is turned to the RUN/START position. The THEFT indicator will turn ON for two seconds, then turn OFF.

If the THEFT indicator flashes for one minute or more, this indicates that there was no key code received. When the vehicle ignition switch is placed in either RUN or START, the PATS module requests the ignition key ID code. The PATS module requests the ignition key ID code by supplying power, ground, and the carrier signal to the transceiver to energize the ignition key. After the energize period, the key transmits its ID code to the transceiver module, which sends it to the PATS module.

The PATS module then compares the received KEY ID code to those stored in memory (16 maximum). If the ID matches, the PATS module sends an enable signal to the PCM over the module communication network.

The passive vehicle protection system utilizes the engine management capabilities of the PCM to enable or disable the vehicle engine. The module communication network is used to send and receive messages to and from the PCM.

Within one second after engine start, the PCM must receive an enable signal from the PATS module through the module communication network or the engine is disabled before the vehicle can be moved.

If the PATS module recognizes a stored ignition key code but there is a module communication network concern preventing the PCM from recognizing the start en able signal from the PATS module, the vehicle engine will be disabled. If this happens, the PATS module will flash the THEFT indicator for one minute, then flash diagnostic trouble code 16 ten times to indicate there is a problem with the module communication network circuits or the PCM is not responding properly.

The passive vehicle protection system will disable the vehicle from starting if there is a:
^ Damaged encoded key.
^ Unprogrammed key.
^ Non-encoded key (key has no electronics).
^ Wiring concern.
^ Transceiver concern.
^ Control module concern.
^ Module communications network concern.