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.
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).
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.
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.
General Information About Fault-tracing In the CAN Network
General information about fault-tracing in the CAN network
The CAN network is a pure communications network and contains no fuses or sensors. The network is divided into two parts: the low speed network
(LS-CAN, Low Speed CAN) and the high speed network (HS-CAN, High Speed CAN). The differences between the networks are their physical position
in the car and the transfer rates. In general terms, HS-CAN is restricted to the engine compartment and LS-CAN to the passenger compartment and the
Both the low speed and the high speed networks have two network resistors installed in two of the control modules. The resistors each have a resistance
of 120 ohms. When taking resistance readings between the two CAN cables, a normal value is approximately 60 ohms. This value can vary between
different vehicles. Permitted values are approximately 55-65 ohms.
Note! Resistance 60 ohms can only be measured if the main artery is intact and connected in the part of the CAN network in which the reading
is taken. If there is an open circuit anywhere along the main artery or if any control module through which the main artery passes (a control
module with four CAN connections) is not connected, resistance will be 120 ohms when the reading is taken. For more information, see the
Diagnostic trouble code (DTC) types
Diagnostic trouble codes (DTCs) which can be stored by control modules connected to the controller area network (CAN) can be split into two
Diagnostic trouble codes (DTCs) DFXX
These diagnostic trouble codes (DTCs) can only be stored in the central electronic module (CEM). This diagnostic trouble code (DTC) is stored when
the central electronic module (CEM) has detected an electrical fault in the controller area network (CAN) wiring, a short-circuit between the controller
area network (CAN) wiring or short-circuit between the controller area network (CAN) wiring and voltage or ground. These diagnostic trouble codes
(DTCs) are not stored if there is an open-circuit in the CAN cable. These diagnostic trouble code do not, in any way, indicate that a fault has occurred in
a control module.
Diagnostic trouble codes (DTCs) 1AXX (Node not alive)
These diagnostic trouble codes can only be stored in the central electronic module (CEM). A trouble code of this type indicates that the central electronic
module (CEM) cannot "hear" a control module on the CAN network from which it anticipates communication. This could be due to an open circuit on