Siren Explanation

SIREN DESCRIPTION
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. This unit is designed to provide the audible alert requirements for the premium VTA.

The alarm siren module consists of microcontroller-based electronic control circuitry, the siren, and a nickel metal hydride backup battery. All of the alarm module components are protected and sealed within a molded plastic housing. An integral connector receptacle (Fig1) #3 extends from the housing and connects the unit to the vehicle electrical system through a dedicated take out and connector of the engine compartment wire harness. The housing also has a threaded insert within a mounting hole through which a screw (Fig 1) #2 secures it to one of two mounting brackets.

A bell-shaped stamped metal mounting bracket (1) is used on vehicles with a diesel engine, while an L-shaped stamped metal mounting bracket is used on vehicles with a gasoline engine. The diesel engine siren and bracket unit is secured by two screws and two spring nuts to the inboard side of the front fender load path beam on the left side of the engine compartment, while the gasoline engine bracket is secured by a single screw and U-nut to an integral stanchion of the molded plastic component tray on the right side of the engine compartment.

The alarm siren module cannot be repaired or adjusted and, if ineffective or damaged, it must be replaced.

SIREN 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 intrusion module over a dedicated serial bus communication circuit. The siren module receives battery voltage on a fused B(+) circuit through a fuse in the Totally Integrated Power Module (TIPM), and receives a path to ground through a ground circuit in the engine compartment wire harness. These connections allow the siren to remain operational, regardless of the ignition switch position.

When the premium version of the Vehicle Theft Alarm (VTA) is armed, the siren module continuously monitors electronic message inputs from the intrusion module 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 state of charge of the siren module backup battery is automatically maintained. The battery is trickle charged approximately 2 minutes during every hour of operation through the battery voltage and ground circuits to the siren module.

The siren will self-detect problems with its internal and external power supply and communication circuits, then send electronic messages indicating the problem to the intrusion module upon receiving an arm or disarm request message. The intrusion module 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 hard wired 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.

SIREN REMOVAL, GASOLINE ENGINE
1. Disconnect and isolate the negative cable from the battery.
2. Locate the alarm siren module (Fig 2) #1 on the component tray on the inboard side of the right front fender load path beam #3.
3. Disconnect the engine compartment wire harness connector from the connector receptacle (Fig 1) #3 of the siren.
4. Remove the screw (Fig 2) #2 that secures the siren mounting bracket to the U-nut and stanchion on the component tray.
5. Remove the siren and mounting bracket from the component tray as a unit.

SIREN INSTALLATION, GASOLINE ENGINE
1. Check to be certain that the U-nut on the component tray stanchion (Fig 2) #4 is in good condition and properly installed.
2. Position the alarm siren module and bracket (Fig 2) #1 to the component tray as a unit.
3. Install and tighten the screw (Fig 2) #2 that secures the siren mounting bracket to the U-nut in the component tray. Tighten the screw to 8 N.m (71 in. lbs.).
4. Reconnect the engine compartment wire harness connector to the connector receptacle (Fig 1) #3 of the siren.
5. Reconnect the negative cable to the battery.