Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Module, Vehicle System Interface (VSIM): Description
The RAM Truck engineered upfitter module called the VSIM (Vehicle System Interface Module) is an available option. Its sales code is "XXS" and "XXSS" and is standard with Ambulance Prep (sales code AH2), a "must have" option with PTO Prep (sales codes LBN or LBV), SSV models, and is available as a stand-alone option. It provides a multitude of useful I/O's to increase upfitter friendliness and upfit simplification. Vehicles not ordered with this option from the factory cannot be retrofitted.
The VSIM serves as a communication gateway between aftermarket or up-fitter control modules and various control modules in the vehicle via CAN-C BUS and makes some of the inputs and outputs of said modules available for specific applications on the VSIM's interface connector.
Concealed and protected within the molded plastic housing of the VSIM is the printed circuit board and the other electronic circuitry of the module. The module contains a microcontroller and communicates with other electronic modules in the vehicle over the Controller Area Network (CAN) data bus system. Two connector receptacles (4) integral to the VSIM housing are connected to the vehicle electrical system through two dedicated take outs and connectors of the instrument panel wire harness.
The VSIM includes an upfitter wire harness kit consisting of four separate color coded harness bundles. Each individual color harness must only be plugged into its corresponding VSIM connector cavity.
A VSIM cannot be adjusted or repaired and, if damaged or ineffective, it must be replaced.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.