Passive Anti-Theft System (PATS) - Principles of Operation

WARNING: This page is about a different car, the 2005 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.

The ignition key read process is initiated by turning the key to the ON or START position. When a valid PATS key is turned to the ON or RUN position the PCM queries the PATS transceiver over circuit 1215 (WH/LG). The transceiver then reads the key code and sends the code to the PCM over circuit 1216 (GY/OG). The PCM then validates the read code against stored authorized keys. If the codes match, the PCM then enables the starter using circuit 1785 (LG/VT) and turns on the anti-theft indicator for 3 seconds by applying ground to circuit 1269 (OG/RD). If the codes do not match, the starter remains disabled and the vehicle will not start. The PCM then illuminates or rapidly flashes the anti-theft indicator by applying ground to circuit 1269 (OG/RD).