Antitheft and Alarm Systems: Description and Operation

VEHICLE THEFT SECURITY SYSTEM
The Vehicle Theft Security System (VTSS) is an available factory-installed option on this model. The VTSS is designed to provide perimeter protection against unauthorized use or tampering by monitoring the vehicle doors 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. If the trigger condition is still present, the lights will continue to flash for an additional 15 minutes, after which time, the system will stop pulsing the lights and return to the "armed" state. The cause of the last 4 alarm triggers is stored by the CTM and may be retrieved by the DRB III . The system may be disarmed by either an unlock command from a valid RKE key fob by using a key in either door, or by using a valid SKIM key in the ignition. The door key cylinders are equipped with disarm switches. There is also a VTSS lamp on the dash that provides information to the driver about the state of the vehicle theft system. (Refer to VEHICLE THEFT SECURITY - DESCRIPTION - SENTRY KEY IMMOBILIZER SYSTEM).

The VTSS includes the following major components, which are described in further detail elsewhere:
- Central Timer Module - The Central Timer Module (CTM) is located on the left cowl side inner panel under the driver side outboard end of the instrument panel. The CTM contains a microprocessor and software that allow it to provide the proper VTSS features and outputs based upon the monitored inputs. The CTM circuitry monitors hard wired switch inputs, as well as message inputs received from other vehicle electronic modules on the Programmable Communications Interface PCI data bus network. (Refer to ELECTRONIC CONTROL MODULES/BODY CONTROL/CENTRAL TIMER MODULE - DESCRIPTION).

- Door Ajar Switch - A door ajar switch is integral to the latch of each door in the vehicle. These switches provide an input to the VTSS indicating whether each door is opened or closed. (Refer to LAMPS/LIGHTING - INTERIOR DOOR AJAR SWITCH - DESCRIPTION).

- Door Cylinder Lock Switch - A door cylinder lock switch is located on the back of each front door lock cylinder. This switch provides an input to the VTSS indicating whether the system should remain armed or be disarmed. (Refer to DOOR CYLINDER LOCK SWITCH - DESCRIPTION).

- Horn Relay - The horn relay is located in the Power Distribution Center (PDC) in the engine compartment near the battery. The horn relay is normally activated by the horn switch to control the sounding of the vehicle horn or horns. However, it I can also be activated by an output of the CTM to provide an audible indication that unauthorized vehicle use or tampering has been detected. (Refer to HORN RELAY - DESCRIPTION).

- Security Indicator - A red Light Emitting Diode (LED) located in the ElectroMechanical Instrument Cluster (EMIC) is illuminated by an output of the CTM to indicate the status of the VTSS or SKIS. This LED is integral to the instrument cluster. (Refer to INSTRUMENT CLUSTER - DESCRIPTION).

Hard wired circuitry connects many of the VTSS components to each other through the electrical system of the vehicle. These hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other, to the vehicle electrical system and to the VTSS components through the use of a combination of soldered splices, splice block connectors, and many different types of wire harness terminal connectors and insulators.

A Central Timer Module (CTM) is used on this model to control and integrate many of the electronic 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 door cylinder lock switch, and the ignition switch. The programming in the CTM allows it to 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 about 3 minutes and flashes the headlamp high beams and security indicator for about 18 minutes or until the system is disarmed, whichever occurs first. The control of these inputs and outputs are what constitute all of the features of the VTSS. Following is information on the operation of each of the VTSS features. Refer to the owner's manual in the vehicle glove box for more information on the features, use and operation of the VTSS.

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 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 locked using the mechanical lock button. Active arming of the VTSS 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. However, once the VTSS arming process has been completed, the ignition switch can be turned to the Accessory position without triggering the alarm.

Pre-arming of the VTSS is initiated when a door is open when the vehicle is locked using a power door lock switch or a key in the door 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 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 is opened, a door is unlocked by any means, or the RKE "Panic" button is depressed during the 17 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, 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 (horn pulsing and headlamps flashing), 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 eighteen minutes). This feature alerts the vehicle operator that the VTSS alarm was activated while the vehicle was unattended.

Sentry Key Immobilizer System
The Sentry Key Immobilizer System (SKIS) is available as a factory-installed option on this model. 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 - The Powertrain Control Module (PCM) is located on the right front fender inner shield above the right front wheel house in the engine compartment.
- Sentry Key Immobilizer Module - The Sentry Key Immobilizer Module (SKIM) is located on the right side of the steering column near the ignition lock cylinder housing and an integral molded plastic antenna ring circles the ignition lock cylinder like a halo. The SKIM and its antenna are concealed beneath the steering column shrouds.
- Sentry Key Transponder - The Sentry Key transponder is molded into the head of the ignition key, and concealed by a gray molded rubber cap.
- Security Indicator - The security indicator is located in the Information Center area of the instrument cluster, to the left of center. (Refer to 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. These hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other, to the vehicle electrical system and to the SKIS components through the use of a combination of soldered splices, splice block connectors, and many different types of wire harness terminal connectors and insulators.

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 electronic messages to communicate with other electronic modules in the vehicle over the Programmable Communications Interface PCI data bus. (Refer to 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 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. The SKIS can be diagnosed, and any stored DTC's can be retrieved using a DRB III scan tool. 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 within a plastic mount into the head of the metal key. In addition to being cut to match the mechanical coding of the ignition lock cylinder, each new Sentry Key has a unique transponder identification code permanently programmed into it by the manufacturer. The Sentry Key transponder cannot be adjusted or repaired. If faulty or damaged, the entire key 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 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.