Error Management In the Controller Area Network (CAN)

Error management in the Controller area network (CAN)

General
The Controller area network (CAN) is monitored and controlled by the central electronic module. When the central electronic module detects a fault in the controller area network a diagnostic trouble code (DTC) is set in the central electronic module. There are different diagnostic trouble codes depending on the type of malfunction detected.
Types of error which are handled are:
- Electrical faults
- No communication from the control module
- Faulty communication.

Electrical faults
In the event of errors in the signal levels on the communication cables for the central electronic module a diagnostic trouble code (DTC) is stored in the central electronic module. A check is carried out on each communication cable to the central electronic module, CAN L, CAN H on the low speed side and CAN L and CAN H on the high speed side There are two different levels which are detected (low or high).
This gives eight diagnostic trouble codes for detecting electrical faults.
The diagnostic trouble codes for electrical faults are CEM-DF0X for the low speed network and CEM-DF1X for high speed network.

No communication from the control module
The central electronic module knows which control modules are in the Controller area network and checks that all the control modules communicate. If any control module on the Controller area network (CAN) does not communicate a diagnostic trouble code is stored in the central electronic module. There is a diagnostic trouble code for each control module. The diagnostic trouble codes are CEM-1A5X respectively CEM-1A6X.

Faulty communication
Each control module except for the central electronic module has two diagnostic trouble code types which are related to faulty communication (the central electronic module only has one type of diagnostic trouble code).
These are:
- Faulty messages
- Configuration fault (missing in the central electronic module (CEM)).

Faulty messages
When a control module sends errors in the messages a number of times, the control module stops communication. The diagnostic trouble code is stored in the control module which caused the faulty message. If the fault is permanent it is impossible to communicate with the control module. It is not possible to read off diagnostic trouble codes from the control module with the switched off communication.
The diagnostic trouble codes (DTCs) are XXX-E000 for the high speed network and XXX-E001 for low speed network.

Configuration fault
If the signal configuration of a control module does not correspond to the signal configuration of the central electronic module, a diagnostic trouble code is stored in the control module with the faulty signal configuration.
The diagnostic trouble code for configuration fault is XXX-E003.