Controller Area Network (Can) System: Function

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 2004 Land Rover Discovery, 2003 Land Rover Discovery, 2002 Land Rover Range Rover, 2002 Land Rover Discovery, and 2001 Land Rover Range Rover. However, it is still accessible from the selected car via links, so may be relevant.

The CAN system uses a twisted pair of wires to form the DATA BUS to minimize electrical interference. This method of serial interface is very reliable and very fast. The information messages are structured so that each of the receivers (ECM or EAT ECU) is able to interpret and react to the messages sent.

The CAN DATA BUS is directly connected between pin 36 of connector C0637 of the ECM and pin 16 of connector C0193 at the EAT ECU, and pin 37 of connector C0637 of the ECM and pin 44 of connector C0193 at the EAT ECU.

The CAN system can fail in the following ways:

CAN data bus wiring open circuit.
CAN data bus wiring short circuit.

In the event of a CAN data bus failure any of the following symptoms may be observed:

MIL illuminated after 2 drive cycles (NAS only).
EAT defaults to 3rd gear only.
Harsh gearshifts.
SPORT and MANUAL lights flash alternately.

Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook/T4. See Fig 1.

Fig 1: Controller Area Network (CAN) System P Codes

Courtesy of LAND ROVER NORTH AMERICA, INC.