Alarm Module: Description and Operation
INTRUSION MODULEDESCRIPTION
An intrusion module (1) 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. This unit is designed to work in conjunction with the intrusion sensor transmitter and intrusion sensor receiver to provide interior motion detection and serves as the interface between the Forward Control Module (FCM), the Electromechanical Instrument Cluster (EMIC) and the alarm siren. The intrusion module has two integral mounts (2) that secure the module. Concealed within the molded plastic housing is the circuitry of the module, which includes a microprocessor.
The intrusion module (2) is secured within a cavity on the right side of a molded plastic intermediate step assembly (1) located on the rear floor panel under the second row seat cushion by two slots and two latch features integral to the floor of the step cavity The module is concealed beneath a carpeted trim cover secured by hook and loop fasteners over the step cavity. The inboard side of this step cavity also contains the satellite radio receiver (4) on vehicles that are so equipped. The module is connected through an integral connector receptacle to the vehicle electrical system by a take out and connector of the body wire harness (3).
The intrusion module unit cannot be adjusted or repaired and, if ineffective or damaged, it must be replaced.
OPERATION
The microprocessor in the intrusion module contains the motion detection logic circuits and controls all of the features of the premium version of the Vehicle Theft Alarm (VTA). The module uses On-Board Diagnostics (OBD) and can communicate with other 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 module to communicate with the Forward Control Module (FCM) and the Electromechanical Instrument Cluster (EMIC). The module also communicates with the alarm siren over a dedicated serial bus circuit.
The intrusion module microprocessor continuously monitors inputs from the intrusion sensor transmitter and receiver as well as inputs from the EMIC and the alarm siren module. The module energizes the intrusion sensor transmitter, which transmits ultrasonic signals into the vehicle cabin through a transmit transducer, then monitors the current draw of the transmitter to detect problems with the transmitter and transmitter circuits. The module also energizes the intrusion sensor receiver, which listens to the ultrasonic signals through a receive transducer as they bounce off of objects in the vehicle interior, then monitors the current draw of the receiver for data signals and to detect problems with the receiver and receiver circuits. If an object is moving in the interior, a detection circuit in the module senses this movement through the modulation of the returning data signals from the receiver.
If movement is detected, the intrusion module sends an electronic message to the FCM over the CAN data bus to flash the exterior lighting and sends another message to the alarm siren module over the dedicated serial bus line to sound the siren. When the EMIC or FCM detect a breach in the perimeter protection through a door, liftgate, flip-up glass, or hood ajar switch input, they send an electronic message to the intrusion module and the module sends a message to the FCM to flash the exterior lighting and a message to the alarm siren module to sound the siren. The module also monitors message 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 module. If a fault does not recur for 50 ignition cycles, the module will automatically erase the stored DTC.
The intrusion module receives battery voltage on a fused B(+) circuit through a fuse in the Junction Block (JB), and is grounded at all times through a hard wired remote ground point. These connections allow the module to remain operational, regardless of the ignition switch position. The hard wired inputs and outputs for the 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 intrusion module, the CAN data bus, or the electronic message inputs to and outputs from the module. The most reliable, efficient, and accurate means to diagnose the intrusion module, the CAN data bus, and the electronic message inputs to and outputs from the module requires the use of a diagnostic scan tool.