Alarm Module: Description and Operation
INTRUSION TRANSCEIVER MODULEFig.5 Intrusion Transceiver Module:
An Intrusion Transceiver Module (ITM) is part of the premium version of the Vehicle Theft Alarm (VTA) in the Vehicle Theft Security System (VTSS). The premium version of the VTA is only available in vehicles built for certain markets, where the additional features offered by this system are required. The ITM is located in the passenger compartment. This unit is designed to provide interior motion detection, and serve as an interface between the Body Control Module (BCM) and the alarm siren module.
Fig.6 Intrusion Transceiver Module:
The ITM is concealed beneath a dedicated molded plastic trim cover that approximates the size and shape of a typical dome lamp housing. However, rather than a lens, the ITM features three sets of louvered openings. One set of louvered openings is located at each outboard end of the center rib, while the third set is centered. Each of the louvered openings is covered on the inside by a sight shield that extends the length of the center rib. The module is secured to a mounting bracket above the headliner.
Concealed within the housing is the circuitry of the ITM which includes a microprocessor, and an ultrasonic receive transducer. Both the transmit transducer on the right side of the module and the receive transducer on the ITM circuit board are aimed through two small round holes in the sight shield of the trim cover. The ITM is connected to the vehicle electrical system by a take out and connector of the overhead wire harness that is integral to the headliner.
The ITM unit cannot be adjusted or repaired and, if faulty or damaged, it must be replaced. The ITM is serviced as a unit with the trim cover.
The microprocessor in the Intrusion Transceiver Module (ITM) contains the motion sensor logic circuits and controls all of the features of the premium version of the Vehicle Theft Alarm (VTA). The ITM uses On-Board Diagnostics (OBD) and can communicate with other modules in the vehicle as well as with the DRB III scan tool using the Programmable Communications Interface (PCI) data bus network. This method of communication is used by the ITM to communicate with the Body Control Module (BCM) and for diagnosis and testing. The ITM also communicates with the alarm siren over a dedicated serial bus circuit.
The ITM microprocessor continuously monitors inputs from its on-board motion sensor as well as inputs from the BCM and the alarm siren module. The ITM motion sensor transmits ultrasonic signals into the vehicle cabin through a transmit transducer, then listens to the returning signals as the bounce OFF of objects in the vehicle interior. If an object is moving in the interior, a detection circuit in the ITM senses this movement through the modulation of the returning ultrasonic signals that occurs due to the Doppler effect. The motion detect function of the ITM can be disabled by depressing the "Lock" button on the Remote Keyless Entry (RKE) transmitter three times within fifteen seconds, while the security indicator is still flashing rapidly or by cycling the key in the driver door cylinder from the center to the lock position. The ITM will signal the alarm siren module to provide a single siren "chirp" as an audible confirmation that the motion sensor function has been disabled.
If movement is detected, the ITM sends an message to the BCM over the PCI data bus to flash the exterior lighting and send a message to the alarm siren module over a dedicated serial bus line to sound the siren. When the BCM detects a breach in the perimeter protection through a door, tailgate, flip-up glass, or hood ajar switch input, it sends an message to the ITM and the ITM sends an message to the BCM over the PCI data bus to flash the exterior lighting and send a message to the alarm siren module over a dedicated serial bus line to sound the siren. The ITM also monitors inputs from the alarm siren module for siren battery or siren input/output circuit tamper alerts, and siren battery condition alerts, then sets active and stored Diagnostic Trouble Codes (DTC) for any monitored system faults it detects. An active fault only remains for the current ignition switch cycle, while a stored fault causes a DTC to be stored in memory by the ITM. If a fault does not reoccur for fifty ignition cycles, the ITM will automatically erase the stored DTC.
The ITM is connected to the vehicle electrical system through the overhead wire harness. The ITM receives battery voltage on a B(+) circuit through a fuse in the Junction Block (JB), and is grounded to the chassis at G303. These connections allow the ITM to remain operational, regardless of the ignition switch position. The hard wired inputs and outputs for the ITM may be diagnosed and tested using conventional diagnostic tools and procedures. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the ITM, the PCI data bus network, or the electronic message inputs to and outputs from the ITM. The most reliable, efficient, and accurate means to diagnose the ITM, the PCI data bus network, and the message inputs to and outputs from the ITM requires the use of a DRB III scan tool. Refer to the appropriate diagnostic information.
Fig.9 Siren Remove/Install:
SIREN
An alarm siren module is part of the premium version of the Vehicle Theft Alarm (VTA) in the Vehicle Theft Security System (VTSS). The premium version of the VTA is only available in vehicles built for certain markets, where the additional features offered by this system are required. The alarm siren module is located in the right front frame rail. This unit is designed to provide the audible alert requirements for the premium VTA.
The alarm siren module consists of microprocessor, the siren, and a nickel metal hydride backup battery. All of the alarm module components are protected and sealed within the housing.
The alarm siren module cannot be repaired or adjusted and, if faulty or damaged, it must be replaced.
The microprocessor within the alarm siren module provides the siren unit features and functions based upon internal programming and arm and disarm messages received from the Intrusion Transceiver Module (ITM) over a dedicated serial bus communication circuit. The alarm siren module will self-detect problems with its internal and external power supply and communication circuits, then send messages indicating the problem to the ITM upon receiving a request from the ITM. The ITM will store a Diagnostic Trouble Code (DTC) for a detected alarm siren module fault that can be retrieved with the DRB III scan tool over the Programmable Communications Interface (PCI) data bus.
When the premium version of the Vehicle Theft Alarm (VTA) is armed, the alarm siren module continuously monitors inputs from the ITM for messages to sound its siren and enters its auto-detect mode. While in the auto-detect mode, if the alarm siren module detects that its power supply or communication circuits are being tampered with or have been sabotaged, it will sound an alarm and continue to operate through its on-board backup battery If the arm siren module is in its disarmed mode when its power supply or communication circuits are interrupted, the siren will not sound. The alarm module will also notify the ITM when the backup battery requires charging, and the ITM will send a message that will allow the backup battery to be charged through the battery voltage and ground circuits to the alarm module only when the ignition switch is in the ON position and the engine is running. This will prevent the charging of the alarm backup battery from depleting the charge in the main vehicle battery while the vehicle is not being operated.
The alarm siren module receives battery voltage through a fuse in the Power Distribution Center (PDC), and is grounded to the chassis. These connections allow the alarm siren module to remain operational, regardless of the ignition switch position. The hard wired inputs and outputs for the alarm siren module may be diagnosed and tested using conventional diagnostic tools and procedures. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the internal circuitry or the backup battery of the alarm siren module, the ITM, the serial bus communication line, or the message inputs to and outputs from the alarm siren module. The most reliable, efficient, and accurate means to diagnose the alarm siren module, the ITM, the serial bus communication line, and the electronic message inputs to and outputs from the alarm siren module requires the use of a DRB III scan tool. Refer to the appropriate diagnostic information.
SENTRY KEY IMMOBILIZER MODULE
The Sentry Key Immobilizer Module (SKIM) is the primary component of the Sentry Key Immobilizer System (SKIS). The SKIM is located in the steering column, below the ignition lock cylinder housing. The SKIM has an integral halo-like antenna ring that extends from one side.
The SKIM cannot be adjusted or repaired. If faulty or damaged, the entire SKIM unit must be replaced.
The Sentry Key Immobilizer Module (SKIM) contains a Radio Frequency (RF) transceiver and a microprocessor. The SKIM transmits RF signals to, and receives RF signals from the Sentry Key transponder through a tuned antenna ring integral to the SKIM housing. If this antenna ring is not mounted properly around the ignition lock cylinder housing, communication problems between the SKIM and the transponder may arise. These communication problems will result in Sentry Key transponder-related faults. The SKIM also communicates over the Programmable Communications Interface (PCI) data bus with the Powertrain Control Module (PCM), the ElectroMechanical Instrument Cluster (EMIC), the Body Control Module (BCM), and/or the DRB III scan tool.
The SKIM retains in memory the ID numbers of any Sentry Key transponder that is programmed into it. A maximum of eight transponders can be programmed into the SKIM. For added system security, each SKIM is programmed with a unique Secret Key code. This code is stored in memory, sent over the PCI data bus to the PCM, and is encoded to the transponder of every Sentry Key that is programmed into the SKIM. Another security code, called a PIN, is used to gain access to the SKIM Secured Access Mode. The Secured Access Mode is required during service to perform the SKIS initialization and Sentry Key transponder programming procedures. The SKIM also stores the Vehicle Identification Number (VIN) in its memory which it learns through a PCI data bus message from the PCM during SKIS initialization.
In the event that a SKIM replacement is required, the Secret Key code can be transferred to the new SKIM from the PCM using the DRB III scan tool and the SKIS replacement procedure. Proper completion of the SKIS initialization will allow the existing Sentry Keys to be programmed into the new SKIM so that new keys will not be required. In the event that the original Secret Key code cannot be recovered, SKIM replacement will also require new Sentry Keys. The DRB III scan tool will alert the technician during the SKIS replacement procedure if new Sentry Keys are required.
When the ignition switch is turned to the ON position, the SKIM transmits an RF signal to the transponder in the ignition key. The SKIM then waits for an RF signal response from the transponder. If the response received identifies the key as valid, the SKIM sends a valid key message to the PCM over the PCI data bus. If the response received identifies the key as invalid, or if no response is received from the key transponder, the SKIM sends an invalid key message to the PCM. The PCM will enable or disable engine operation based upon the status of the SKIM messages. It is important to note that the default condition in the PCM is an invalid key; therefore, if no message is received from the SKIM by the PCM, the engine will be disabled and the vehicle immobilized after two seconds of running.
The SKIM also sends indicator light status messages to the EMIC over the PCI data bus to tell the EMIC how to operate the SKIS indicator. This indicator light status message tells the EMIC to turn the indicator ON for about three seconds each time the ignition switch is turned to the ON position as a bulb test. After completion of the bulb test, the SKIM sends indicator light status messages to the EMIC to turn the indicator OFF, turn the indicator ON, or to flash the indicator ON and OFF. If the SKIS indicator lamp flashes or stays ON solid after the bulb test, it signifies a SKIS fault. If the SKIM detects a system malfunction and/or the SKIS has become inoperative, the SKIS indicator will stay ON solid. If the SKIM detects an invalid key or if a key transponder-related fault exists, the SKIS indicator will flash. If the vehicle is equipped with the Customer Learn transponder programming feature, the SKIM will also send messages to the EMIC to flash the SKIS indicator lamp, and to the BCM to generate a single audible chime tone whenever the Customer Learn programming mode is being utilized. (Refer to ELECTRICAL/VEHICLE THEFT SECURITY - 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) in SKIM memory if a system malfunction is detected. The SKIM can be diagnosed, and any stored DTC's can be retrieved using a DRB III scan tool. Refer to the appropriate diagnostic information.