Part 2

Diagnostic trouble codes (DTCs) E000 and E001 in a control module (E000=HS-CAN, E001=LS-CAN)
Diagnostic trouble code (DTC) E001 indicates a fault in the data communication on the CAN network. This can be due to interference of various types or if a control module is sending incorrect messages. Monitoring for this type of fault takes place continuously. The diagnostic trouble codes (DTCs) are originally intended to indicate contact bounces of if incorrect messages are sent over the network, but can also be stored in the event of a short-circuit between the two CAN cables or if communication only functions on one of the two cables. It takes a couple of seconds from the fault occurring to its detection.
Another important cause of these codes is if a control module has been disconnected from the network without the battery cable having been disconnected from the negative terminal (in such cases removing the ignition key does not help) or if the signal on the CAN cables is "weak" or disrupted. This can occur if communication is only working on one of the CAN cables or if one of the network resistors in the network is not working. The network resistors on the low speed network are located in the upper electronic module (UEM) and the rear electronic module (REM). On the high speed network, the resistors are located in the anti-lock brake system module (ABS)/brake control module (BCM) and in the electronic throttle module (ETM), except for Bosch EMS MY02 and later where the resistors are located in the brake control module (BCM) and the engine control module (ECM).
In certain cases, the diagnostic trouble code (DTC) may be stored if a control module sends data at the wrong transfer speed or if the crystal in a control module is defective.

Diagnostic trouble codes (DTCs) in the event of lost signal, rapid indication of faults on the CAN network
Some control modules, such as the engine control module (ECM), the electronic throttle module (ETM), the anti-lock brake system module (ABS) and the transmission control module (TCM) continually check the existence of each other and store diagnostic trouble codes (DTCs) in the event of missing signals. These diagnostic trouble codes (DTCs) are often due to different driving conditions and combinations of diagnostic trouble codes (DTCs) are often stored which can make fault-tracing more difficult. When attempting to recreate the fault, there is no guarantee that the same combination of diagnostic trouble codes (DTCs) will be stored. The detection of these diagnostic trouble codes (DTCs) is often more sensitive and they are usually stored more easily than CEM-1A51 to CEM-1A66 or CEM-DF03 to CEM-DF16. This can therefore be an indication of a short-term intermittent fault having occurred on the CAN network.
Below is a selection of diagnostic trouble codes (DTCs) that may or may not be stored in the event of an intermittent fault on the CAN network:
- ECM-928C (Bosch), ECM-922A (Denso), only when the engine is running. These diagnostic trouble codes (DTCs) indicate that the control signal for the cruise control is missing or could not be received by the engine control module (ECM)
- ECM-901A, ECM-901E, ECM-902A, ECM-911A, ECM-912A and ECM-913A for Bosch and ECM-901A, ECM-902A, ECM-911A, ECM-912A for Denso
- SRS-00D6, time-out for the seat belt buckle. This diagnostic trouble code (DTC) indicates that the supplemental restraints system module (SRS) has not received the status of the seat belt buckles from the central electronic module (CEM). The sensor for the seat belt buckles is directly linked to the central electronic module (CEM)
- SRS-00D5, status of the SRS indicator lamp in the driver information module (DIM)
- Discrepancies in the signal from the pedal position sensor between the directly connected signal and the signal over the CAN network. See the table below.






Multiple diagnostic trouble codes (DTCs) and extended diagnostics (counters and freeze frames)
The detection time for faults in the CAN network varies depending on the diagnostic trouble code (DTC). This means that for different fault occurrences, different diagnostic trouble codes (DTCs) can be stored in different control modules. Several diagnostic trouble codes (DTCs) in different control modules can be confusing and must be investigated at the start of fault-tracing to check for any link between the various codes.
It is now possible to read off extended diagnostic trouble code (DTC) information in VIDA, normally counters and frozen values. This can also help with fault-tracing on the CAN network as it can provide information about diagnostic trouble codes (DTCs) that are stored simultaneously. Remember that the function using counters can be implemented differently in different control modules, which can make it difficult to compare cycles between different control modules.
When performing fault-tracing on a car with many intermittent E003 and CEM-1A51 to CEM-1A66 diagnostic trouble codes (DTCs), this can be made easier by checking the affected control modules. Copy the diagram in the service manual, Data communication for the relevant car model, and write down all diagnostic trouble codes (DTCs) and counters at the relevant control modules. Check any conclusions can be drawn from where the diagnostic trouble codes (DTCs) are stored. If the diagnostic trouble codes (DTCs) are in control modules at one end of the CAN network, this can give an indication of where the fault may be located.

Limp-home modes and characteristics of control modules in the event of faults in the CAN network
When a control module cannot receive messages from the central electronic module (CEM) it will go into Limp-home mode. In such cases, the control module can retain part of its functionality. The remaining functionality varies in different control modules. If a fault occurs after a control module has been started up, it will normally retain the most recent values as the Limp-home values. There are exceptions, such as the fuel gauge in the driver information module (DIM).
Some clear examples for the low speed side network:
- Driver information module (DIM):
As the driver information module (DIM) only displays signals received from the CAN network, it will soon be evident if signals are lost. The display of various signals will disappear at slightly different times due to some filtering of the signals in the driver information module (DIM). The values on the gauges are normally frozen for around ten seconds before dropping to zero and the driver information module (DIM) shuts down. If only one control module has disappeared from the network, the driver information module (DIM) can display the first indication of this. An example of this is where the rear electronic module (REM) stops communicating, which is indicated by the fuel gauge dropping to zero
- Climate control module (CCM):
This control module must retain some of its functionality even if the CAN communication is lost. It is also a very good indication of whether the CAN communication has been lost, as the LEDs will light up exactly ten seconds after the ignition key has been turned to positions one or two. Other symptoms: if the AC compressor is not working, apart from the first second when the function is checked by the engine control module (ECM), this can indicate a fault in the climate control module (CCM)>central electronic module (CEM)>engine control module (ECM) chain. Another very obvious symptom is that the blower fan continues to operate for up to ten minutes after the key is removed from the ignition switch. This is because the climate control module (CCM) is powered via Extended-X from the central electronic module (CEM). The climate control module (CCM) normally switches off the blower fan and other functions when it does not receive a signal over the CAN network after the ignition key has been removed. If there is no CAN communication, the climate control module (CCM) will continue to operate until the central electronic module (CEM) switches off the power supply
- Driver door module (DDM)/Passenger door module (PDM):
The module will be set to a resting mode and no functions will be performed, such as setting the mirror or operating the power windows
- Power seat module (PSM):
The memory function in the seat will not work. Stored positions for seats and mirrors will not work when the car is unlocked with a remote control
- Upper electronic module (UEM):
The seat belt reminder will be lit, even though the belt is secured in the seat belt buckle. It will not be possible to lock or unlock the car using the remote control
- Audio module (AUM):
The radio retains most of its functionality. However, the buttons on the steering wheel will not work
- Rear electronic module (REM):
The fuel gauge is not working and it will not be possible to lock/unlock the rear doors using the central locking switch. The heating loops in the rear windshield and the rear folding head restraints will not work
- Steering wheel angle sensor module (SAS):
The anti-skid system will not work
- Steering wheel module (SWM):
Buttons on the steering wheel and the turn signal lamp stalk will not work. However the horn will still work because it is connected directly to the central electronic module (CEM).

Some clear examples for the high speed network:
- Engines:
Cannot be started as a result of no communication between the central electronic module (CEM) and transmission control module (TCM) + engine control module (ECM)
- Electronic throttle module (ETM):
The node has three Limp-home levels:
- Level 1: No cruise control function
- Level 2: Accelerator pedal "heavy". Poor response
- Level 3: Present Limp-home mode. The engine speed (RPM) is controlled via the injectors.
- Transmission control module (TCM):
It is not possible to use all the gears.

Note! If the control module has gone into Limp-home due to an open-circuit in the CAN communication, the functionality will not return during the cycle, even in the event of the fault disappearing.

- Anti-lock brake system module(ABS)/Brake control module (BCM):
The remaining functionality depends on what fault has occurred. In the event of a fault in the AYC sensor, the indicator lamp lights and DSTC stops working. Faults in the wheel sensors cause the indicator lamp to light and the ABS function to disappear, although there is still braking assistance. The unit can lose certain diagnostics in Limp-home mode
- Central electronic module (CEM):
Extremely large loss of function. It is worth noting that the control module has separate circuits for the high speed and low speed networks. This means that it is possible to communicate with the control module via the high speed network even when the low speed network has a fault.