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

MODEL 211 with ENGINES 647.961, 648.961 

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 transfer between individual control units
• Readying sensor signals for several systems
• Reducing the number of electric cables
• 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 lines of the data line must not be mixed up (low level/high level). The CDI control unit always represents a terminal in terms of bus adaptation.

A 120 Ω terminating resistor should therefore be installed in the CDI 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 kbits/s) engine CAN data bus (CAN CAN-C) for the drive and chassis systems and the slightly slower (83.3 kbit/s) body CAN data bus. (CAN-B) structure for the vehicle interior.

For external vehicle diagnosis using STAR DIAGNOSIS a CAN data bus diagnosis (CAN-D) with a speed of 500 kbit/s is also available.

The interface between the three CAN data buses (Gateway) is located in the central gateway control unit.

The instrument cluster, electronic ignition switch control unit and the steering column module are connected with both the body CAN data bus and the engine CAN data bus and exchange data with both data bus systems. But they do not act 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" (O  pen systems and their I  nterfaces for E  lectronics in motor vehicles) is used for all control units of the CAN data bus.

CDI control unit component description

N3/9

GF07.16-P-6000IC