Anti-Theft-Passive Anti-Theft System (PATS): Notes

WARNING: This page is about a different car, the 2004 Mercury Monterey and 2004 Ford Freestar. However, it is still accessible from the selected car via links, so may be relevant.

The passive anti-theft system (PATS) uses radio frequency identification technology to deter a driveaway 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 powertrain control module (PCM) before it can be used to start the engine. There are special diagnostic procedures described in this article 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 transceiver module communicates with the PATS key. This module is located in the steering column attached to the ignition cylinder housing. During each vehicle start sequence, the transceiver module reads the PATS key identification code and sends the data to the PCM. The PCM validates the code as correct and enables the starter.

The control function is 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 starter enable signal. The PCM initiates the key interrogation sequence when the PATS key is inserted in the ignition switch and when the switch is turned to RUN or START.

The PCM enables or disables 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.

PATS uses a visual theft indicator. This 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 (for more than 3 seconds) when the ignition switch is turned to RUN or START.

The PATS is not compatible with non-Ford approved 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.