INTRUSION TRANSCEIVER MODULE

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 Controller Area Network (CAN) data bus. This method of communication is used by the ITM to communicate with the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) 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 EMIC 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 through a receive transducer 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 status message to the EMIC over the CAN data bus and sends an electronic message to the alarm siren module over a dedicated serial bus line to sound the siren. Then the EMIC relays an electronic request message to the Totally Integrated Power Module (TIPM) to flash the exterior lighting. When the EMIC detects a breach in the perimeter protection through a hard wired door or liftgate ajar switch input or receives a hood ajar switch input from the TIPM, it sends an electronic message to the ITM and the ITM 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 headliner wire harness. The ITM receives battery current through a fuse in the TIPM, and receives ground through the body wire harness. 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.