Vehicle System Interface Module - Operation

OPERATION

The microcontroller-based electronic Vehicle System Interface Module (VSIM) (also known as the Vehicle Systems Integration Module/VSIM or the aftermarket module) contains the electronic logic circuitry and software that enable many of the aftermarket equipment and systems typically installed on police or fleet vehicles to communicate with and be integrated with the electronic control modules and features already installed in the vehicle. The VSIM can communicate with aftermarket modules or with other electronic modules in the vehicle using the Controller Area Network (CAN) data bus.

The VSIM is powered by a fused B(+) circuit and is grounded at all times so that it can operate regardless of the ignition switch position. The module awakens or sleeps based upon the status of the CAN data bus network. The module monitors both active and stored Diagnostic Trouble Codes (DTC) through On-Board Diagnostics (OBD) and communicates with a diagnostic scan tool using the CAN data bus.

The hard wired inputs and outputs of the VSIM 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 electronic controls and communication between modules and other devices that provide some features of the VSIM. The most reliable, efficient and accurate means to diagnose the VSIM or the electronic controls and communication related to operation of the aftermarket systems connected through the VSIM requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.