Vehicle Theft Security: Operation

The Vehicle Theft Security System (VTSS) is divided into two basic subsystems: Vehicle Theft Alarm (VTA) and Sentry Key Immobilizer System (SKIS). Following are paragraphs that briefly describe the operation of each of these two subsystems.

Vehicle Theft Alarm -  The Body Control Module (BCM) is used to control many of the electronic functions and features included in the Vehicle Theft Alarm (VTA). The BCM receives hard wired inputs indicating the status of the door ajar switches, the door cylinder lock switches, the ignition switch, the tailgate ajar switch, the tailgate cylinder lock switch, the flip-up glass ajar switch, the power lock switches and, in vehicles built for certain markets where it is required, the hood ajar switch. The programming in the BCM allows it to process the information from all of these inputs and send control outputs to energize or de-energize the combination flasher, the horn relay (except vehicles with the Export premium version of the VTA), and the security indicator. In addition, in vehicles built for certain markets where the Export premium version of the VTA is required, the BCM also exchanges electronic messages with the Intrusion Transceiver Module (ITM) over the Programmable Communications Interface (PCI) data bus network to provide the features found in this version of the VTA.

The hard wired circuits and components of the VTA may be diagnosed and tested using conventional diagnostic tools and procedures. However, conventional diagnostic methods may not prove conclusive in the diagnosis of the Body Control Module (BCM), the ElectroMechanical Instrument Cluster (EMIC), the Intrusion Transceiver Module (ITM), or the Programmable Communications Interface (PCI) data bus network. The most reliable, efficient, and accurate means to diagnose the BCM, the EMIC, the ITM, and the PCI data bus network inputs and outputs related to the VTA requires the use of a DRBIII(R) scan tool. Refer to the appropriate diagnostic information. Following are paragraphs that briefly describe the operation of each of the VTA features. See the owner's manual in the vehicle glove box for more information on the features, use and operation of the VTA.

• Enabling -  The BCM must have the VTA function electronically enabled in order for the VTA to perform as designed. The logic in the BCM keeps its VTA function dormant until it is enabled using a DRBIII(R) scan tool. The VTA function of the BCM is enabled on vehicles equipped with the VTA option at the factory, but a service replacement BCM must be VTA-enabled by the dealer using a DRBIII(R) scan tool.
• Pre-Arming -  The VTA has a pre-arming sequence. Pre-arming occurs when a door, the tailgate, or the flip-up glass is open when the vehicle is locked using a power lock switch, or when the "Lock" button on the Remote Keyless Entry (RKE) transmitter is depressed. The power lock switch will not initiate the pre-arming sequence if the key is in the ignition switch. When the VTA is pre-armed, the arming sequence is delayed until all of the doors, the tailgate, and the flip-up glass are closed.
• Arming -  Passive arming of the VTA occurs when the vehicle is exited with the key removed from the ignition switch and the doors are locked while they are open using the power lock switch (see Pre-Arming). Active arming of the VTA occurs when the "Lock" button on the Remote Keyless Entry (RKE) transmitter is depressed to lock the vehicle after all of the doors, the tailgate, and the flip-up glass are closed. The VTA will not arm if the doors are locked using the key in a lock cylinder or using a mechanical lock button. Once the VTA begins the passive or active arming sequence, the security indicator in the instrument cluster will flash rapidly for about sixteen seconds. This indicates that the VTA arming sequence is in progress. If the ignition switch is turned to the On position, if a door is unlocked with the power lock switch or the RKE transmitter, or if the tailgate is unlocked by any means during the sixteen second arming sequence, the security indicator will stop flashing and the VTA arming sequence will abort. On vehicles equipped with the hood ajar switch, the VTA arming sequence will occur regardless of whether the hood is open or closed, but the underhood area will not be protected unless the hood is closed when the VTA arming sequence begins. Also, if the status of the hood ajar switch changes from open to closed during the sixteen second arming sequence, the security indicator will stop flashing and the VTA arming sequence will abort. Once the sixteen second arming sequence is successfully completed, the security indicator will flash at a slower rate, indicating that the VTA is armed.
• Disarming -  For vehicles built for the North American market, disarming of the VTA occurs when the vehicle is unlocked using the key to unlock a door or the tailgate. Disarming of the VTA for any market also occurs when the vehicle is unlocked by depressing the "Unlock" button of the Remote Keyless Entry (RKE) transmitter, or by turning the ignition switch to the On position using a valid Sentry Key Immobilizer System (SKIS) key. Once the alarm has been activated, any of these disarming methods will also deactivate the alarm.
• Power-Up Mode -  When the armed VTA senses that the battery has been disconnected and reconnected, it enters its power-up mode. In the power-up mode the alarm system returns to the mode that was last selected prior to the battery failure or disconnect. If the VTA was armed prior to the battery disconnect or failure, the technician or vehicle operator will have to actively or passively disarm the system after the battery is reconnected. The power-up mode will also apply if the battery goes dead while the system is armed, and battery jump-starting is then attempted. The VTA will remain armed until the technician or vehicle operator has actively or passively disarmed the system. If the VTA is in the disarmed mode prior to a battery disconnect or failure, it will remain disarmed after the battery is reconnected or replaced, or if jump-starting is attempted.
• Alarm -  The VTA alarm output varies by the version of the VTA with which the vehicle is equipped. In all cases, the alarm provides both visual and audible outputs; however, the time intervals of these outputs vary by the requirements of the market for which the vehicle is manufactured. In all cases, the visual output will be a flashing on and off of the exterior lamps. For vehicles equipped with the North American or the Export base version of the VTA, the audible output will be a pulsing of the horn. For vehicles with the Export premium version of the VTA, the audible output will be a cycling of the alarm siren. See the owner's manual in the vehicle glove box for details of the alarm output requirements of the specific market for which the vehicle was manufactured. The inputs that will trigger the alarm include the door ajar switches, the tailgate ajar switch, the flip-up glass ajar switch, and in vehicles built for certain markets where they are required, the hood ajar switch and the Intrusion Transceiver Module (ITM).
• Tamper Alert -  The VTA tamper alert feature will pulse the horn (or the alarm siren for the Export premium version of the VTA) three times upon VTA disarming, if the alarm was triggered and has since timed-out. This feature alerts the vehicle operator that the VTA alarm was activated while the vehicle was unattended.
• Intrusion Alarm -  The intrusion alarm is an exclusive feature of the Export premium version of the VTA, which is only available in certain markets where it is required. When the VTA is armed, a motion sensor in the Intrusion Transceiver Module (ITM) monitors the interior of the vehicle for movement. If motion is detected, the ITM sends an electronic message to the BCM over the PCI data bus to invoke the visual alarm feature, and sends an electronic message to the alarm siren in the engine compartment over a dedicated serial bus to invoke the audible alarm feature. The motion detect feature of the ITM can be disabled by depressing the "Lock" button on the RKE transmitter three times within fifteen seconds during VTA arming, while the security indicator is still flashing rapidly. The VTA provides a single short siren "chirp" as an audible confirmation that the motion detect disable request has been received. The ITM must be electronically enabled in order for the intrusion alarm to perform as designed. The logic in the ITM keeps its intrusion alarm function dormant until it is enabled using a DRBIII(R) scan tool. The intrusion alarm function of the ITM is enabled on vehicles equipped with this option at the factory, but a service replacement ITM must be configured and enabled by the dealer using a DRBIII(R) scan tool.

Sentry Key Immobilizer System -  The Sentry Key Immobilizer System (SKIS) is designed to provide passive protection against unauthorized vehicle use by disabling the engine after about two seconds of running, whenever any method other than a valid Sentry Key is used to start the vehicle. The SKIS is considered a passive protection system because it is always active when the ignition system is energized and does not require any customer intervention. The SKIS uses Radio Frequency (RF) communication to obtain confirmation that the key in the ignition switch is a valid key for operating the vehicle. The microprocessor-based SKIS hardware and software also use electronic messages to communicate with other electronic modules in the vehicle over the Programmable Communications Interface (PCI) data bus. See ELECTRONIC CONTROL MODULES article.

Pre-programmed Sentry Key transponders are provided with the vehicle from the factory. Each Sentry Key Immobilizer Module (SKIM) will recognize a maximum of eight Sentry Keys. If the customer would like additional keys other than those provided with the vehicle, they may be purchased from any authorized dealer. These additional keys must be programmed to the SKIM in the vehicle in order for the system to recognize them as valid keys. This can be done by the dealer using a DRBIII(R) scan tool or, if Customer Learn programming is an available SKIS feature in the market where the vehicle was purchased, the customer can program the additional keys, as long as at least two valid Sentry Keys are already available. See STANDARD PROCEDURE - SENTRY KEY TRANSPONDER PROGRAMMING  .

The SKIS performs a self-test each time the ignition switch is turned to the On position, and will store fault information in the form of Diagnostic Trouble Codes (DTC's) if a system malfunction is detected. The SKIS can be diagnosed, and any stored DTC's can be retrieved using a DRBIII(R) scan tool.