Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Principles of Operation: Notes
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. This system is known as SecuriLock in North America, Safeguard in the U.K., and PATS in continental Europe.
The PATS uses a specially encoded ignition key. Each encoded ignition key contains a permanently installed electronic device called a transponder. Each transponder contains a unique electronic identification code out of over four quadrillion possible combinations.
Each encoded ignition key must be programmed into the vehicle's powertrain control module (PCM) before it can be used to start the engine. There are special diagnostic repair procedures described that must be carried out if a new encoded ignition key is necessary.
The PATS transceiver communicates with the encoded ignition key. The PATS transceiver is located behind the steering wheel column shroud and contains an antenna connected to a small electronics module. During each vehicle start sequence, the transceiver reads the encoded ignition key identification code and sends data to the PCM.
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 encoded ignition 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. The indicator will prove out for three 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 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 carrying out an investigation of PATS-related no-start issues.
The PATS will be activated and will disable the vehicle from starting if there is:
- an incorrectly encoded ignition key.
- a damaged encoded ignition key.
- an unprogrammed key.
- a non-encoded key (key has no electronics).
- damaged wiring.
- damaged PATS transceiver.
- damaged PCM.
- a module communications network concern.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.