Antitheft and Alarm Systems: Description and Operation

VEHICLE THEFT SECURITY SYSTEM
The Vehicle Theft/Security System (VTSS) is designed to protect against whole vehicle theft. The system monitors vehicle doors, hood, liftgate, and ignition for unauthorized operation.The VTSS activates:
- Sounding of the horn.
- Flashing of the park lamps.
- Flashing of the headlamps.

The RKE Module has three modes of operation including CUSTOMER USAGE mode, DEALER LOT STORAGE mode, and SHIPPING MODE.

The customer usage mode provides full functionality of the module and is the mode in which the RKE Module should be operating when used by the customer. Dealer lot storage mode and shipping mode are reduced power modes meant to extend vehicle battery life during shipping and storage in the dealer lot. Dealer lot storage mode provides limited VTSS and power door lock functions, and disables the Remote Keyless Entry (RKE) functions. This mode is intended to be used when the vehicle is on the dealer lot to provide VTSS coverage of the vehicle while minimizing battery drain. Shipping mode disables all normal functions of the module with the exception of communications over the vehicle's PCI bus, and is intended to be used when the vehicle is shipped from the assembly plant. The dealer must remove the module from shipping mode and place it into either the dealer lot storage or customer usage modes of operation.

NOTE: The dealer must remove the module from "SHIP MODE" and place the RKE Module into either the "DEALER LOT" storage or "CUSTOMER USAGE" modes of operation after receiving the vehicle from the assembly plant. Refer to Switching Operating Modes/Configuring a New Module under Service Procedures.

Once in the CUSTOMER USAGE mode of operation, the system is armed when the vehicle is locked using the:
- Power door lock switches.
- Remote Keyless Entry (RKE) transmitter.
- Key cylinder switches.

After the vehicle is locked and the last door is closed, the circular red VTSS indicator in the instrument cluster will flash quickly for 16 seconds, indicating that arming is in progress. If no monitored systems are activated during this period (excluding the hood), the system will arm. After 16 seconds, the LED will continue to flash at a slower rate indicating the system is armed.

If the hood ajar switch is not sensed by the system, the indicator LED will remain lit during the arming process, although the system will still arm. If the VTSS indicator does not illuminate at all upon door closing, it indicates that the system is not arming. THE SYSTEM WILL NOT ARM IF THE HOOD IS OPEN (switch is grounded), or the decklid security switch (knockout) is not grounded.

VTSS disarming occurs upon normal vehicle entry by unlocking either door or liftgate via the key cylinders or RKE transmitter, or by starting the vehicle with a valid Sentry Key. This disarming will also halt the alarm once it has been activated.

A tamper alert exists to notify the driver that the system had been activated. This alert consists of 3 horn pulses when the vehicle is disarmed.

The VTSS will not arm by mechanically locking the vehicle doors. This will manually override the system.

All of the sensors for the VTSS system can be monitored using the DRB III scan tool. The DRB III is also useful to determine the cause of a customer complaint of the alarm sounding for no apparent reason.

NOTE: In the dealer lot storage mode of operation, all of the above descriptions of the VTSS are true with the following exceptions:
- Remote Keyless Entry functions are disabled, and cannot be used for arming/disarming the VTSS.
- The VTSS indicator is non-operational.

SENTRY KEY IMMOBILIZER SYSTEM
The Sentry Key Immobilizer System (SKIS) is available as a factory-installed option on this vehicle. It is designed to provide passive protection against unauthorized vehicle use by disabling the engine, after two (2) seconds of running, whenever an invalid key is used to start the vehicle. The engine kill feature on domestic vehicles is accomplished via the Sentry Key Immobilizer Module (SKIM). The SKIS is active whenever the ignition is ON and does not require any customer intervention. The primary components of the system are the Sentry Key Immobilizer Module (SKIM), Sentry Key (ignition key with a transponder molded into the head), indicator light, and the Powertrain Control Module (PCM). The SKIM is mounted to the steering column with the molded, integral antenna mounted on the light halo surrounding the ignition lock cylinder. The indicator light, is located in the instrument cluster.

The SKIS includes keys from the factory which are pre-programmed. Each SKIM will recognize a maximum of eight Sentry Keys. If the customer would like to own additional keys other than those provided with the vehicle, they can be purchased from any authorized dealer. These keys must be programmed to the SKIM on the vehicle in order for the system to recognize them as valid keys. This can be done by the dealer with a DRB III scan tool or by a customer if this feature is available in their market and they have two (2) valid keys already available to them. Refer to the Service Procedures portion of this system for additional details. The SKIS performs a self-test each time the ignition switch is turned to the ON position and will store 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 as described in the appropriate Body Diagnostic Procedures.

SKIS OPERATION
When ignition power is supplied to the SKIM, the SKIM performs an internal self-test. After the self-test is completed, the SKIM energizes the antenna (this activates the transponder chip) and sends a challenge to the transponder chip. The transponder chip responds to the challenge by generating an encrypted response message using the following:

Secret Key - This is an electronically stored value (identification number) that is unique to each SKIS. The secret key is stored in the SKIM, PCM and all ignition key transponders.

Challenge - This is a random number that is generated by the SKIM at each ignition key cycle.

The secret key and challenge are the two variables used in the algorithm that produces the encrypted response message. The transponder uses the crypto algorithm to receive, decode and respond to the message sent by SKIM. After responding to the coded message, the transponder sends a transponder ID message to the SKIM. The SKIM compares the transponder ID to the available valid key codes in SKIM memory (8 key maximum). After validating the ignition key the SKIM sends a PCI Bus message called a "Seed Request" to the powertrain controller then waits for a powertrain controller response. If the powertrain controller does not respond, the SKIM will send the seed request again. After three failed attempts the SKIM will stop sending the seed request and store a trouble code. If the powertrain controller sends a seed response, the SKIM sends a valid/invalid key message to the powertrain controller. This is an encrypted message that is generated using the following:

VIN - Vehicle Identification Number.

Seed - This is a random number that is generated by the PCM at each ignition key cycle.

The VIN and seed are the two variables used in the rolling code algorithm that encrypts the "valid/invalid key" message. The powertrain controller uses the rolling code algorithm to receive, decode and respond to the valid/invalid key message sent by SKIM. After sending the valid/invalid key message the SKIM waits 3.5 seconds for an PCM status message from the powertrain controller. If the PCM does not respond with a valid key message to the SKIM, a fault is detected and a trouble code stored.

The SKIS incorporates a Red Warning lamp located in the Instrument Cluster. The lamp is illuminated when the SKIM sends a PCI Bus message to the instrument cluster requesting the lamp ON. The SKIM will request lamp operation for the following:
- bulb check at ignition ON
- to alert the vehicle operator to a SKIS malfunction
- customer key programming mode

For all faults except transponder faults and VIN mismatch, the lamp remains on steady. In the event of a transponder fault the light flashes at the rate of 1 Hz (once per second). If a fault is present the lamp will remain ON or flashing for the complete ignition cycle.

If a fault is stored in SKIM memory which prevents the system from operating properly, the PCM will allow the engine to start and run (for 2 seconds) up to six times. After the sixth attempt, the PCM will not allow the engine to start until the fault is corrected.

SKIS INDICATOR LAMP
The Sentry Key Immobilizer System (SKIS) uses an indicator light to convey information on the status of the system to the customer. This light is shared with the Vehicle Theft Security System (VTSS). The light is located in the instrument cluster and is shared with the Vehicle Theft Security System. The indicator light is controlled by the instrument cluster based upon messages it receives from the Sentry Key Immobilizer Module (SKIM) on the PCI bus.

The SKIM sends messages to the instrument cluster to turn the light ON for three (3) seconds when the ignition switch is turned to the ON position as a power-up test. After completion of the power-up test, the SKIM sends a message on the PCI bus to keep the light OFF for a duration of one second. Then, the SKIM sends messages to the instrument cluster to operate the light based upon the results of the SKIS self tests. The light may be actuated in two possible ways, flashing or on solid. If the light comes ON and stays ON solid after a power-up test, this indicates that the SKIM has detected a system malfunction. If the SKIM detects an invalid key when the ignition switch is moved to the ON position, it sends a message on the PCI bus to flash the light. The SKIM can also send a message to flash the light and generate a single audible chime at the same time. These two events occurring simultaneously indicate that the SKIS has been placed into the "Customer Learn" mode. Refer to Electrical, Vehicle Theft Security, Transponder Key, Standard Procedure - Sentry Key Immobilizer System Transponder programming for more information on the "Customer Learn" mode. If the light comes ON and stays ON after the power-up test, diagnosis of the SKIS should be performed using a DRB III scan tool and the appropriate Body Diagnostic Procedures. The light is not a serviceable component.

TRANSPONDER KEY

Sentry Key Immobilizer Transponder:

The Sentry Key Immobilizer System (SKIS) uses a transponder chip that is integral to each ignition key to communicate with the Sentry Key Immobilizer Module (SKIM). Ignition keys are supplied with the vehicle when it is shipped from the factory. The transponder chip is undermolded within the head of the key. This undermold is hidden beneath an overmolded rubber cap.

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 as well. 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 also permanently programmed into the transponder's memory. Therefore, blank keys for the SKIS must be programmed by the SKIM in addition to being cut to match the mechanical coding of the ignition lock cylinder. Refer to Electrical, Vehicle Theft Security, Transponder Key, Standard Procedure - Transponder Programming.

The Sentry Key's transponder is within the range of the SKIM's transceiver antenna ring when it is inserted into the ignition lock cylinder. When the ignition switch is turned to the ON position, the SKIM communicates with the Sentry Key via a radio frequency (RF) signal. The SKIM determines if a valid key is present based on the information it receives from the Sentry Key. If a valid key is detected, that fact is communicated to the PCM via the PCI bus and the vehicle is allowed to continue running. If an invalid key is received by the PCM or no status at all is communicated, the vehicle will stall after two (2) seconds of running. The indicator light will be flashing at this point. The Sentry Key's transponder can not be repaired. If it is faulty or damaged, it must be replaced.