Antitheft and Alarm Systems: Description and Operation
VEHICLE THEFT SECURITYVehicle Theft Security System
The Vehicle Theft Security System (VTSS) is designed to protect against whole vehicle theft. The system monitors vehicle doors, deck lid key cylinder, and ignition action for unauthorized operation. The alarm activates:
- Sounding of the horn
- Flashing of the park and tail lamps
- Flashing of the headlamps
- An engine kill feature (without SKIS)
Upon failure of proper VTSS/SKIM communication to the PCM, the PCM will shut OFF fuel after two seconds of run time. The engine will not re-crank on the key cycle that the failure occurred, a full key down sequence must be performed for the engine to crank again. After six consecutive fuel shut-offs, the engine will no longer crank on subsequent key cycles. The failure must be corrected and a valid communication process between the BCM (VTSS), or SKIM, and the PCM must occur for the engine to crank and start again.
The electronics for the VTSS are part of the Body Control Module (BCM). The system is armed when the vehicle is locked using the:
- Power door lock switches
- Remote Keyless Entry transmitter.
- Door Cylinder Lock Switches.
For vehicles equipped with SKIS, the doors do not have to be locked to enable the fuel shut OFF feature.
After the vehicle is locked and the last door is closed, the set LED indicator in the top cover will flash quickly for 16 seconds, indicating that arming is in progress. If no monitored systems are activated during this period, the system will arm. After 16 seconds the indicator LED will continue to flash at a slower rate.
This indicates that the system is armed. If the deck lid key cylinder 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 indicator LED does not illuminate at all upon door closing it indicates that the system is not arming.
Passive disarming occurs upon normal vehicle entry by unlocking either door with the ignition key/remote transmitter. This disarming will also halt the alarm once it has been activated.
A tamper alert exists to notify the driver that the VTSS had been activated. This alert consists of 3 horn pulses when the vehicle is disarmed.
NOTE: The VTSS will not arm by pushing down the door lock mechanism. This will manually override the system.
For Door Cylinder Lock Switch Removal and Installation, refer to Electrical, Power Locks, Door Cylinder Lock Switch.
Sentry Key Immobilizer Module Location:
Sentry Key Immobilizer System
The Sentry Key Immobilizer System (SKIS) is designed to provide passive protection against unauthorized vehicle use by preventing the engine from operating. The components of this system are the Sentry Key Immobilizer Module (SKIM), Body Control Module (BCM), Sentry Key transponder, VTSS indicator LED, and the Powertrain Control Module (PCM).
The SKIM is installed on the steering column near the ignition lock cylinder. The transponder is located under the molded rubber cap on the head of the ignition key. The VTSS indicator LED is located in the instrument panel top cover.
The SKIS includes two valid Sentry Key transponders from the factory. These two Sentry Keys can be used to program additional non-coded blank Sentry Keys. These blank keys can be cut to match a valid ignition key, but the engine will not start unless the key transponder is also programmed to the vehicle. The SKIS will recognize no more than eight valid Sentry Key transponders at any one time.
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 can be retrieved using a DRB III scan tool as described in the proper Body Diagnostic Procedures.
Triggering The VTSS
Any of the following actions will trigger the system:
1. Opening any door.
2. Removing the deck lid lock cylinder.
3. Turning the ignition to the ON position.
Using the power door switch or the keyless transmitter will arm the system.
CAUTION: The VTSS indicator LED will trigger and engine will continue to run if the vehicle is equipped with SKIS and the proper key is used to start the vehicle. This condition will occur if the VTSS has been triggered.
NOTE: The ignition switch can be turned to the accessory position without triggering alarm system.
SKIS INDICATOR LAMP
The Sentry Key Immobilizer System (SKIS) uses the Vehicle Theft Security System (VTSS) indicator LED to give an indication when the SKIS is faulty or when the vehicle has been immobilized due to the use of an invalid ignition key. The LED is controlled by the BCM based upon messages received from the Sentry Key Immobilizer Module (SKIM). The VTSS/SKIS indicator LED is hard wired directly to the BCM.
The SKIM sends messages to the BCM to turn the LED on for about three seconds when the ignition switch is turned to the ON position as a bulb test. After completion of the bulb test, the SKIM sends bus messages to the BCM to keep the LED OFF for a duration of about one second. Then the SKIM sends messages to the BCM to turn the LED ON or OFF based upon the results of the SKIS self-tests. If the VTSS indicator LED comes on and stays ON after the bulb test, it indicates that the SKIM has detected a system malfunction and/or that the SKIS has become inoperative. If the SKIM detects an invalid key when the ignition switch is turned to the ON position, it sends messages to the BCM to flash the VTSS indicator LED.
The SKIM can also send messages to the BCM to flash the LED and to generate a single audible chime tone. These functions serve as an indication to the customer that the SKIS has been placed in its "Customer Learn" programming mode. See Sentry Key Immobilizer System Transponder Programming for more information on the "Customer Learn" programming mode.
The VTSS indicator LED is housed in the Automatic Temperature Control (ATC) Sun Sensor located in the instrument panel top cover. Refer to Instrument Panel and Systems for service of ATC Sun Sensor. If the VTSS indicator LED comes ON and stays ON after the bulb test function, diagnosis of the SKIS should be performed with a DRB III scan tool and the proper Body Diagnostic Procedures.
Sentry Key Immobilizer Transponder:
TRANSPONDER KEY
The Sentry Key Immobilizer System (SKIS) uses a transponder that is integral to each of two ignition key that are supplied with the vehicle when it is shipped from the factory. The transponder chip is insulated within a nylon mount inserted in the head of the key, and invisible beneath a molded rubber cap.
Each Sentry Key transponder has a unique transponder identification code programmed into it by the manufacturer. The Sentry Key Immobilizer Module (SKIM) has a unique "Secret Key" code programmed into it by the manufacturer. When a Sentry Key transponder is programmed into the memory of the SKIM, the SKIM learns the transponder identification code from the transponder, and the transponder learns the "Secret Key" code from the SKIM. Each of these codes is stored within the transponder and in the nonvolatile memory of the SKIM. Therefore, blank keys for the SKIS must be programmed by and into the SKIM, in addition to being cut to match the mechanical coding of the ignition lock cylinder. See Sentry Key Immobilizer System Transponder Programming for more information.
The Sentry Key transponder is within the range of the SKIM transceiver antenna ring when it is inserted in the ignition lock cylinder. When the ignition switch is turned to the START or ON positions, the SKIM transceiver issues a Radio Frequency (RF) signal that excites the transponder chip. The transponder chip responds by issuing an RF signal containing its transponder identification code and the "Secret Key" code. The SKIM transceiver compares the transponder codes with the codes stored in its memory to determine whether a valid key is in the ignition lock cylinder.
The Sentry Key transponder cannot be repaired and, if faulty or damaged, it must be replaced.
VTSS INDICATOR
The Sentry Key Immobilizer System (SKIS) the Vehicle Theft Security System (VTSS) indicator LED to give an indication when the SKIS is faulty or when the vehicle has been immobilized due to the use of an invalid ignition key. The LED is controlled by the BCM based upon messages received from the Sentry Key Immobilizer Module (SKIM). The VTSS/SKIS indicator LED is hard wired directly to the BCM.
The SKIM sends messages to the BCM to turn the LED on for about three seconds when the ignition switch is turned to the ON position as a bulb test. After completion of the bulb test, the SKIM sends bus messages to the BCM to keep the LED OFF for a duration of about one second. Then the SKIM sends messages to the BCM to turn the LED ON or OFF based upon the results of the SKIS self-tests. If the VTSS indicator LED comes ON and stays ON after the bulb test, it indicates that the SKIM has detected a system malfunction and/or that the SKIS has become inoperative. If the SKIM detects an invalid key when the ignition switch is turned to the ON position, it sends messages to the BCM to flash the VTSS indicator LED.
The SKIM can also send messages to the BCM to flash the LED and to generate a single audible chime tone. These functions serve as an indication to the customer that the SKIS has been placed in its "Customer Learn" programming mode. See Sentry Key Immobilizer System Transponder Programming for more information on the "Customer Learn" programming mode.
The VTSS indicator LED is housed in the Automatic Temperature Control (ATC) Sun Sensor located in the instrument panel top cover. Refer to Instrument Panel and Systems for service of ATC Sun Sensor. If the VTSS indicator LED comes ON and stays ON after the bulb test function, diagnosis of the SKIS should be performed with a DRB III scan tool and the proper Body Diagnostic Procedures.