INTRUSION TRANSCEIVER MODULE
DESCRIPTION
An Intrusion Transceiver Module (ITM) (1) is part of the export premium version of the Vehicle Theft Alarm (VTA) in the Vehicle Theft Security System (VTSS). The export 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, on the lower surface of the headliner (2) near the center of the vehicle. This component is designed to provide interior motion detection, and serve as an interface between the Body Control Module (BCM) and the alarm siren module.
The ITM is concealed beneath a molded plastic trim cover (1) that approximates the size and shape of a typical dome lamp housing. Rather than a lens, the trim cover features three sets of louvered openings. Each of the louvered openings is covered on the inside by a single molded black plastic sight shield that extends the length of the center rib for appearance. The entire module is secured to a molded plastic mounting bracket above the headliner. Besides the ITM, the trim cover also conceals two plastic pins integral to the mounting bracket that are used to secure the bracket to the headliner with two stamped nuts that are installed from below. An adhesive-backed foam pad is installed above the ITM bracket between the headliner and the roof panel to provide additional headliner stabilization and support for the ITM mounting. Two small notch-like service holes (5) on the rear edge of the trim cover afford access to the two integral rear latches (6) of the ITM housing (3) for service removal.
Concealed within the housing is the electronic circuitry of the ITM which includes a microprocessor, and an ultrasonic receive transducer. A molded plastic connector receptacle (2) containing six terminal pins that is soldered to a small circuit board and extends through a clearance hole in the left front corner of the ITM housing, and an ultrasonic transmit transducer housing extends from the center of the right side of the ITM housing. 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 wire harness that is integral to the headliner.
The ITM unit cannot be adjusted or repaired and, if ineffective or damaged, it must be replaced.
OPERATION
The microprocessor in the Intrusion Transceiver Module (ITM) contains the motion sensor logic circuits and controls all of the features of the export premium version of the Vehicle Theft Alarm (VTA). The ITM uses On-Board Diagnostics (OBD) and can communicate with other electronic modules in the vehicle as well as with a diagnostic 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 through the 16-way data link connector located on the driver side lower edge of the instrument panel. The ITM also communicates with the alarm siren module over a dedicated serial bus circuit.
The ITM microprocessor continuously monitors inputs from its on-board motion sensor circuitry as well as inputs from the BCM and the alarm siren module. The on-board ITM motion sensor circuitry transmits ultrasonic signals into the vehicle cabin through a transmit transducer, then listens to the returning signals as they 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 15 seconds while the VTA is arming (security indicator is flashing rapidly). 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 while the VTA is armed, the ITM sends an electronic message to the BCM over the PCI data bus to flash the exterior lighting and sends an electronic 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 electronic message to the ITM and the ITM sends an electronic message to the BCM over the PCI data bus to flash the exterior lighting and sends an electronic 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 for 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 recur for 50 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 current through a fuse in the Junction Block (JB), and receives ground through the body wire harness from a ground screw located at the base of the left D-pillar behind the quarter trim panel. These connections allow the ITM to remain operational, regardless of the ignition switch position.
The hard wired circuits of the ITM may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the ITM or the electronic controls or communication between modules and other devices that provide some features of the VTA. The most reliable, efficient, and accurate means to diagnose the ITM or the electronic controls and communication related to ITM operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.
REMOVAL
1. Disconnect and isolate the battery negative cable.
2. While lightly pulling downward on either rear corner of the Intrusion Transceiver Module (ITM) trim cover (4), insert a small thin-bladed screwdriver (1) through each of the service holes (3) on the rear edge of the trim cover to depress and release the two integral rear latch features of the module from the mounting bracket above the headliner (2).
3. Pull the ITM trim cover rearward far enough to disengage the two integral front latch features of the module from the mounting bracket above the headliner.
4. Pull the ITM and trim cover down from the headliner far enough to access and disconnect the overhead wire harness connector for the ITM from the module connector receptacle.
5. Remove the ITM from the headliner.
INSTALLATION
1. Position the Intrusion Transceiver Module (ITM) to the headliner (3).
2. Reconnect the overhead wire harness connector for the ITM to the module connector receptacle.
3. Align the two front latch features of the ITM with the mounting bracket (2) above the headliner.
4. Push the ITM trim cover forward far enough to insert the two integral rear latch features of the module into the two rear latch receptacles (4) of the mounting bracket above the headliner.
5. Push upward firmly and evenly on the rear edge of the ITM trim cover until the two rear latch features of the module are engaged in the mounting bracket above the headliner.
6. Reconnect the battery negative cable.
NOTE: If the Intrusion Transceiver Module (ITM) has been replaced with a new unit, the new ITM MUST be initialized before the Vehicle Theft Security System can operate as designed. The use of a diagnostic scan tool is required to initialize the ITM. Refer to the appropriate diagnostic information.