Description And Operation: Operation
The microcontroller within the alarm siren module provides the siren unit features and functions based upon internal programming and electronic arm and disarm messages received from the BCM over a LIN data bus connection. The BCM monitors inputs from the Ultrasonic and Anti-tilt Module (UAM) to control the output to the alarm siren module. The siren module receives battery voltage on a fused B(+) circuit through a fuse in the BCM and receives a path to ground through a ground circuit in the headlamp and dash wire harness. These connections allow the siren to remain operational, regardless of the status of the ignition.
When the premium version of the Vehicle Theft Alarm (VTA) is armed, the siren module continuously monitors electronic message inputs from the BCM to sound its internal siren. While armed, the siren also enters its auto-detect mode. While in the auto-detect mode, if the siren module detects that its power supply or communication circuits are being tampered with or have been sabotaged, it will sound an audible alarm and continue to operate through an on-board backup battery. If the siren module is in its disarmed mode when its power supply or communication circuits are interrupted, the siren will not sound.
The alarm siren module will also notify the BCM when the backup battery requires charging, and the BCM will send electronic messages that will allow the backup battery to be recharged through the battery voltage and ground circuits to the alarm siren module only while the status of the ignition is On and the engine is running. This prevents the potential discharge of the main battery while the vehicle is not being operated.
The alarm siren module will self-detect problems with its internal and external power supply and communication circuits, then send electronic messages indicating the problem to the BCM upon receiving an arm or disarm request message. The BCM will store a Diagnostic Trouble Code (DTC) for any detected alarm siren module fault. The DTC can then be retrieved with a diagnostic scan tool through the 16-way Data Link Connector (DLC) located under the driver side lower edge of the instrument panel over the Controller Area Network (CAN) data bus.
The hardwired inputs and outputs for the alarm siren module 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 alarm siren module or the electronic controls and communication between other modules and devices that provide some features of the VTA system. The most reliable, efficient and accurate means to diagnose the alarm siren module or the electronic controls and communication related to alarm siren module operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.