Body Control Module - Description and Operation - Sprinter 2500 V6-30L Diesel Turbo (2008)
Body Control Module: Description and Operation
Module-Programmable Special
Description
DESCRIPTION
The Programmable Special Module (PSM) is the interface between the vehicle and the body manufacturer. It enables specific manufacturer functions
such as working speed control. The PSM can transmit information received via Controller Area Network (CAN) messages, either to discrete outputs or
to the body CAN bus. The PSM is also able to transmit discrete inputs or information from the body CAN bus to the interior CAN bus. It configures the
type and direction of information and inputs using a diagnostic scan tool.
The PSM (8) is located under the driver seat in the seat riser assembly. It can be accessed for service by removing the driver seat and seat riser cover,
See: Service and Repair/Module-Programmable Special/Removal.
Operation
OPERATION
In modern networked vehicles it is becoming increasingly difficult to intervene in the on-board electrical system for modifications, or retrofitting not
done by the vehicle manufacturer. The conventional hardwired 12 volt switched circuit is no longer feasible in these vehicles.
Today, switches are connected close to the fitted control module and deliver voltage-coded or bitcoded signals over network bus circuits. In control
modules these signals are mostly converted into Controller Area Network (CAN) messages and transmitted on the CAN data bus circuit. A second
control unit installed close to the actuator (lamp, motor, valve.) receives this signal and energizes the actuator with the operating current.
An intervention in the on-board electrical system is only possible with the Programmable Special Module (PSM). The PSM can transmit and receive
messages over the vehicle CAN data bus circuit. The PSM is connected to the CAN B BUS and access to the CAN C BUS is accomplished through the
gateway function of the EZS.
As a result messages containing the following can be received and sent by the PSM:
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commands (e.g. switch on rear fog lamp)
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status reports (e.g. right sliding door open)
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measurement values (e.g. outside air temperature 21°C)
