Antitheft and Alarm Systems: Description and Operation

VEHICLE THEFT SECURITY SYSTEM
The VTSS is designed to provide perimeter protection against unauthorized use or tampering by monitoring the vehicle doors, the liftgate, and the ignition system. If unauthorized use or tampering is detected, the system responds by pulsing the horn and flashing the headlamp high beams. If the vehicle is also equipped with the optional Sentry Key Immobilizer System (SKIS), which provides passive vehicle protection by preventing the engine from operating unless a valid electronically encoded key is detected in the ignition lock cylinder, the VTSS will also disable the engine from operating until the system is disarmed. (Refer to ELECTRICAL/VEHICLE THEFT SECURITY - DESCRIPTION - SENTRY KEY IMMOBILIZER SYSTEM).

The VTSS includes the following major components, which are described in further detail elsewhere in this service information:
- Central Timer Module (Refer to ELECTRICAL/ELECTRONIC CONTROL MODULES/BODY CONTROL/CENTRAL TIMER MODULE - DESCRIPTION).
- Door Ajar Switch (Refer to ELECTRICAL/LAMPS/LIGHTING - INTERIOR/DOOR AJAR SWITCH - DESCRIPTION).
- Door Cylinder Lock Switch (Refer to ELECTRICAL/POWER LOCKS/DOOR CYLINDER LOCK SWITCH - DESCRIPTION).
- Horn Relay (Refer to ELECTRICAL/HORN/ HORN RELAY - DESCRIPTION).
- Liftgate Ajar Switch(Refer to ELECTRICAL/LAMPS/LIGHTING - INTERIOR/DOOR AJAR SWITCH - DESCRIPTION - LIFTGATE AJAR SWITCH).
- Liftgate Cylinder Lock Switch (Refer to ELECTRICAL/POWER LOCKS/LIFTGATE CYLINDER LOCK SWITCH - DESCRIPTION).
- Security Indicator(Refer to ELECTRICAL/INSTRUMENT CLUSTER - DESCRIPTION).

A Central Timer Module (CTM) is used on this model to control and integrate many of the functions and features included in the Vehicle Theft Security System (VTSS). In the VTSS, the CTM receives inputs indicating the status of the door ajar switches, the liftgate ajar switch, the door cylinder lock switch, the liftgate cylinder lock switch, and the ignition switch. The CTM will process the information from all of these inputs and send control outputs to energize or de-energize the horn relay the headlamp high beams, and the security indicator. If the VTSS alarm is triggered, the CTM pulses the horn for 3 minutes and flashes the headlamp high beams and security indicator for 18 minutes or until the system is disarmed. Following is information on the operation of each of the VTSS features.

Enabling
The CTM must have the VTSS function electronically enabled in order for the VTSS to perform as designed. The logic in the CTM keeps its VTSS function dormant until it is enabled using a DRB III scan tool. The VTSS function of the CTM is enabled on vehicles equipped with the VTSS option at the factory, but a service replacement CTM must be VTSS-enabled by the dealer using a DRB III scan tool. Refer to the appropriate diagnostic information.

Arming
Passive arming of the VTSS occurs when the vehicle is exited with the key removed from the ignition switch, the headlamps are turned OFF, and the doors are locked while they are open using the power lock switch, or locked after they are closed by turning either front door or the liftgate lock cylinder to the lock position using the key. The power lock switch will not function if the key is in the ignition switch or the headlamps are turned ON with the driver side front door open. The VTSS will not arm if the doors are closed and locked using the mechanical lock button. Active arming of the VTSS also occurs when the "Lock" button on the Remote Keyless Entry (RKE) transmitter is depressed to lock the vehicle. For active arming to occur, the doors must be closed and the ignition switch must be in the OFF position when the RKE transmitter "Lock" button is depressed.

Pre-arming of the VTSS is initiated when a door or the liftgate is open when the vehicle is locked using a power door lock switch or a key in the door or liftgate lock cylinder (passive), or when the RKE transmitter "Lock" button is depressed (active). Pre-arming will not occur if the key is in the ignition switch or the headlamps are turned ON with the driver side front door open. When the VTSS is pre-armed, the arming sequence is delayed until all of the doors and the liftgate have been closed. The VTSS will remain in Prearmed mode for up to 17 seconds after all doors and lift gate have been closed.

Once the VTSS begins the passive or active arming sequence, the security indicator in the instrument cluster will flash rapidly for about 17 seconds. This indicates that the VTSS arming is in progress. If the ignition switch is turned to the ON position, a door or the liftgate is opened, a door or the liftgate is unlocked by any means, or the RKE "Panic" button is depressed during the seventeen second arming process, the security indicator will stop flashing and the arming process will abort. Once the 17-second arming sequence is successfully completed, the security indicator will flash at a slower rate, indicating that the VTSS is armed.

Disarming
Passive disarming of the VTSS occurs when the vehicle is unlocked using the key to unlock either front door or the liftgate and, if the vehicle is equipped with the optional Sentry Key Immobilizer System (SKIS), by turning the ignition switch to the ON position using a valid SKIS key Active disarming of the VTSS occurs when the vehicle is unlocked by depressing the "Unlock" button of the RKE transmitter. Once the alarm has been activated either disarming method will also deactivate the alarm. Depressing the "Panic" button on the RKE transmitter will not disarm the VTSS.

Power-up Mode
When the armed VTSS senses that the battery has been disconnected and reconnected, it enters its power-up mode. In the power-up mode the alarm system remains armed following a battery failure or disconnect. If the VTSS was armed prior to a battery disconnect or failure, the technician or vehicle operator will have to actively or passively disarm the alarm 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 attempted. The VTSS will be armed until the technician or vehicle operator has actively or passively disarmed the alarm system. If the VTSS 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.

Tamper Alert
The VTSS tamper alert feature will sound the horn three times upon disarming, if the alarm was triggered and has since timed-out (about 18 minutes) or if the battery has been disconnected and reconnected. This feature alerts the vehicle operator that the VTSS alarm was activated while the vehicle was unattended.

SENTRY KEY IMMOBILIZER SYSTEM
Vehicles equipped with this option can be readily identified by a gray molded rubber cap on the head of the ignition key. Models not equipped with SKIS have a black molded rubber cap on the head of the ignition key.

The SKIS includes the following major components, which are described in further detail elsewhere in this service information:
- Powertrain Control Module
- Sentry Key Immobilizer Module (Refer to ELECTRICAL/VEHICLE THEFT SECURITY - OPERATION)
- Sentry Key Transponder
- Security Indicator(Refer to ELECTRICAL/INSTRUMENT CLUSTER/SECURITY INDICATOR - DESCRIPTION).

Except for the Sentry Key transponders, which rely upon Radio Frequency (RF) communication, hard wired circuitry connects the SKIS components to the electrical system of the vehicle.

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 uses messages to communicate with other modules in the vehicle over the Programmable Communications Interface (PCI) data bus. (Refer to ELECTRICAL/ELECTRONIC CONTROL MODULES/COMMUNICATION - OPERATION).

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 DRB III 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. (Refer to ELECTRICAL/VEHICLE THEFT SECURITY - STANDARD PROCEDURE - 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. Refer to the appropriate diagnostic information.

Sentry Key Immobilizer Transponder:

TRANSPONDER KEY
Each ignition key used in the Sentry Key Immobilizer System (SKIS) has an integral transponder chip. Ignition keys with this feature can be readily identified by a gray rubber cap molded onto the head of the key while conventional ignition keys have a black molded rubber cap. The transponder chip is concealed beneath the molded rubber cap, where it is molded into the head of the metal key Each new Sentry Key has a unique transponder identification code permanently programmed into it by the manufacturer. The Sentry Key transponder if faulty or damaged, must be replaced.

When the ignition switch is turned to the ON position, the Sentry Key Immobilizer Module (SKIM) communicates through its antenna with the Sentry Key transponder using a Radio Frequency (RF) signal. The SKIM then listens for a RF response from the transponder through the same antenna. The Sentry Key transponder chip is within the range of the SKIM transceiver antenna ring when it is inserted into the ignition lock cylinder. The SKIM determines whether a valid key is present in the ignition lock cylinder based upon the response from the transponder. If a valid key is detected, that fact is communicated by the SKIM to the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus, and the PCM allows the engine to continue running. If the PCM receives an invalid key message, or receives no message from the SKIM over the PCI data bus, the engine will be disabled after about two seconds of operation. The ElectroMechanical Instrument Cluster (EMIC) will also respond to the invalid key message on the PCI data bus by flashing the security indicator ON and OFF.

Each Sentry Key has a unique transponder identification code permanently programmed into it by the manufacturer. Likewise, the SKIM has a unique Secret Key code programmed into it by the manufacturer. When a Sentry Key is programmed into the memory of the SKIM, the SKIM stores the transponder identification code from the Sentry Key, and the Sentry Key learns the Secret Key code from the SKIM. Once the Sentry Key learns the Secret Key code of the SKIM, it is permanently stored in the memory of the transponder. Therefore, once a Sentry Key has been programmed to a particular vehicle, it cannot be used on any other vehicle. (Refer to ELECTRICAL/VEHICLE THEFT SECURITY - STANDARD PROCEDURE - TRANSPONDER PROGRAMMING).

The SKIS performs a self-test each time the ignition switch is turned to the ON position, and will store key-related fault information in the form of Diagnostic Trouble Codes (DTC's) in SKIM memory if a Sentry Key transponder problem is detected. The Sentry Key transponder chip can be diagnosed, and any stored DTC's can be retrieved using a DRB III scan tool. Refer to the appropriate diagnostic information.