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DESCRIPTION AND OPERATION
Anti-Theft - Passive Anti-Theft System (PATS)
The passive anti-theft system (PATS) contains the following components:
anti-theft indicator
encoded ignition key
PATS transceiver
instrument cluster
powertrain control module (PCM)
The 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 encoded ignition 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 encoded ignition key must be programmed into the vehicle's PCM, before it can be used to start the engine. There are special diagnostic procedures outlined in the workshop manual that must be carried out if new encoded ignition keys are to be installed. Refer to GENERAL PROCEDURES.
The encoded key is larger than a traditional ignition key. The key does not require batteries and should last the life of the vehicle.
The PATS transceiver communicates with the encoded ignition key. The PATS transceiver is located behind the steering 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 the 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 engine enable. The PCM initiates the key interrogation sequence when the vehicle ignition switch is turned to the RUN or START position.
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 does not start.
The PATS uses a visual anti-theft indicator. This indicator proves out for 3 seconds when the ignition switch is turned to the RUN or the START position 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 the RUN or START position. PATS also "blips" the theft indicator every 2 seconds at ignition OFF to act as a visual theft 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 investigation of PATS-related no-start issues.
Passive Anti-Theft System (PATS) - Principles of Operation
The passive anti-theft system (PATS) is initiated by turning the ignition switch to the ON or START position. When a valid PATS key is turned to the ON or RUN position the powertrain control module (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 enables the starter motor through circuit 1419 (LG/YE). If the codes do not match, the starter remains disabled and the vehicle does not start. The PCM then flashes or turns on the anti-theft warning indicator lamp to indicate the fault.
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Monday, December 1st, 2008 AT 12:50 PM
