Anti-Theft—Passive
The passive anti-theft system (PATS) contains the following components:
theft indicator
encoded ignition key
transceiver module
instrument cluster
powertrain control module (PCM)
standard corporate protocol (SCP) communication network
starter relay
The PATS uses radio frequency identification technology to deter a driveaway 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. This information can be found in customer literature such as the Owners Guide.
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 instrument cluster before it can be used to start the engine. There are special diagnostic procedures outlined in the manual that must be performed if the encoded ignition keys need to be replaced.
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 transceiver module communicates with the encoded ignition key. This module is located behind the steering column shroud and contains an antenna connected to a small electronics module. During each vehicle start sequence, the transceiver module reads the encoded ignition key identification code and sends the data to the instrument cluster.
The control functions are contained in the instrument cluster. This module performs all of the PATS functions such as receiving the identification code from the encoded ignition key and controlling the engine enable. The instrument cluster initiates the key interrogation sequence when the vehicle ignition switch is turned to RUN or START.
The PATS uses the PCM to enable or disable the engine. The instrument cluster communicates with the PCM over the SCP communication network in order to enable engine operation. The instrument cluster and the PCM use sophisticated messages in order to prevent a theft. The instrument cluster and the PCM share security data when first installed together that makes them a matched pair. After this security data sharing, these modules will not function in other vehicles. The shared PCM ID is remembered even if the battery is disconnected. The instrument cluster also stores the vehicle's key identification code even if the battery is disconnected. There are special diagnostic procedures outlined in this workshop manual that may be performed if either the instrument cluster or the PCM needs replacement.
All elements of PATS must be functional before the engine is allowed to start. If any of the components are not working properly, the vehicle will not start.
PATS uses a visual theft indicator. This 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 (for more than three seconds) when the ignition switch is turned to RUN or START. PATS also "blips" the theft indicator every two seconds at ignition OFF to act as a visual theft deterrent.
PATS differs from perimeter anti-theft systems in that PATS enables and disables the engine from starting. If equipped, the perimeter anti-theft system protects the perimeter of the vehicle (doors, hood and trunk) and sounds an alarm.
PATS also disables the starter motor in addition to the PCM disabling the engine. When PATS disables the vehicle, it will neither crank nor start. If the instrument cluster is removed from the vehicle, the engine will not crank.
The starter relay is used as an additional means of disabling the vehicle engine. The starter relay is disabled when the PATS cannot read a valid encoded ignition key at ignition ON. The PATS will not store a diagnostic trouble code (DTC) or flash the theft indicator if a valid encoded ignition key is read but a fault occurs in the starter relay circuit.
The PATS is not compatible with after market remote start system, 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. | 
