CAN data bus, function - GF54.00-P-0005GM

MODEL 463 up to 31.5.12 with ENGINE 113.993

Fig 1: Identifying CAN Data Bus Function Diagram

Courtesy of MERCEDES-BENZ USA

CAN stands for "C ontroller A rea N etwork". This is an electrical bus system for carrying data over two wires.

The tasks are:

Data interchange between the individual control units
Readying sensor signals for several systems
Reducing the number of wires
Improving the electromagnetic compatibility (EMC)

The CAN data bus consists of a special twisted two-core data line that connects all CAN users (control units) in parallel.

The two wires of the data line must not be mixed up (low level / high level). The motor electronics (N3/10) control unit is always a consumer with regard to bus adaptation.

A 120 Ω terminating resistor is therefore installed in the motor electronics control unit.

The data are transmitted digitally over the CAN databus at various intervals. The individual data blocks are defined in a data protocol and it is specified which data are received or transmitted by a control unit. Each connected control unit is able to transmit or receive data (bidirectional bus).

The sum of the data blocks, the short break between two transmission intervals and additional properties of the CAN data bus are checked constantly. Detected faults are stored and placed in the fault memory.

In the vehicle a distinction is made between a fast (500 kbit/s) engine CAN data bus (CAN-C) for the drive systems and chassis systems and the slower (83.3 kbit/s) body CAN data bus (CAN-B) structure for the vehicle interior.

The interface of the two CAN data buses (Gateway) is located in the EIS [EZS] control unit (N73).

The instrument cluster (A1) and steering column module (N80) are connected both with the body CAN data bus and with the engine CAN data bus and exchange data with both data bus systems. However, they do not serve as an interface (gateway) between both data bus systems!

When a control unit is replaced, the new control unit must be coded again.

This control unit coding is possible via a STAR DIAGNOSIS menu.

The international standardized network management "OSEK" (open systems and their interfaces for electronics in vehicles) is used for all control units on the CAN data bus.

ME-SFI control unit, location/task/design/function

GF07.61-P-5000AM