Faulty Communication: Notes

The diagnostic trouble code (DTC) is stored in the event of communication faults on the high speed side of the control area network (CAN). There can be a number of causes for faults in the communication:

• Intermittent open-circuit in one or both CAN cables in part of the network
• Intermittent short-circuits between the CAN cables
• Intermittent short-circuits between one of the CAN cables and ground or supply voltage
• Fault in the communication circuit in one or more control modules
• Internal fault in a control module on the CAN network that results in the control module transmitting faulty messages on the CAN network.

In the event of a diagnostic trouble code (DTC) for a communication fault in the relevant control module, any diagnostic trouble codes (DTCs) in the central electronic module (CEM) must also be checked. The central electronic module (CEM) monitors the voltage level in the CAN cables. The central electronic module (CEM) is the only control module that can directly store a diagnostic trouble code (DTC) for a short-circuit in one of the cables for ground or supply voltage. Do not replace the central electronic module (CEM) in the event of a CAN fault unless fault-tracing has indicated that the central electronic module (CEM) has an internal fault.

In order to check the control area network (CAN) cables, the resistance in the network must be measured.

Other information 

• see GENERAL INFORMATION ABOUT FAULT-TRACING IN THE CAN NETWORK

• Continue 

  Refer to TAKING READING ON CABLE IN THE CAN NETWORK (HS-CAN)