1. Engine compartment CAN test
Test 1.1: Procedure in case of CAN faults
Test 1.2: Evaluation of CAN fault codes
Test 1.3: Further CAN test options
1.1. Procedure in case of CAN faults
Test 1.1.1: How do I quickly reach my goal?
Test 1.1.2: General test information
Test 1.1.3: General CAN fundamentals
Test 1.1.4: Possible aids and their usage
1.1.1. How do I quickly reach my goal?
How do I quickly reach my goal?First call up menu item 'Evaluation of CAN fault codes' in case of CAN timeout fault codes and communication
errors.The resulting tests must be performed.Menu item 'Further CAN test options' should only be called up if the above-specified tests do not
produce the desired result.Note:Menu item 'General test information' can be called up for an explanation of the different CAN fault types.
1.1.2. General test information
Notes on CAN fault codes:CAN timeout fault
- A CAN timeout fault code is set due to the absence of a CAN input signal.The cause of this may be not only the transmitter control unit, but
also the CAN networking.
- For example:No CAN message was received from control unit A.
Bus OFF fault
- A Bus OFF fault code is set, when the control unit cannot send a certain amount of messages to the CAN bus or the messages are
incomplete.The control unit then switches off for a short time from CAN bus.
- For example:CAN controller: CAN bus OFF
Functional CAN fault
- A functional CAN fault code is set because of an implausible CAN input signal.The cause of this is not the CAN networking, but the
transmitter control unit or its sensors.
- For example:CAN signal 'A' from control unit B is implausible.
Notes on CAN faults that cannot be read out as fault codes.Bus wake-up event
- An event that wakes up the bus without reason is designated a bus wake-up event.
- The cause of this is not the CAN networking, but the transmitter control unit or its sensors.
- Further possible causes of fault:
- Magnetic fields caused by nearby high-voltage installations, railroad installations or power plants.
- Magnetic fields can radiate on to lines and control units in rare cases and cause undefined behavior in the control units.
- The special tool 'Star Diagnosis CANtool' can be used to log bus wake-up events, bus keepawake events and other signals.
Bus keepawake event
- When a control unit keeps communication on the bus awake without reason, this is designated a bus keepawake event.
- The cause of this is not the CAN networking, but the transmitter control unit or its sensors.
- Further possible causes of fault:
- Magnetic fields caused by nearby high-voltage installations, railroad installations or power plants.
- Magnetic fields can radiate on to lines and control units in rare cases and cause undefined behavior in the control units.
- The special tool 'Star Diagnosis CANtool' can be used to log bus wake-up events, bus keepawake events and other signals.
1.1.2. No further information available.
1.1.3. General CAN fundamentals
Test 1.1.3.1: Low-Speed CAN (83,3 kBit/s)
Test 1.1.3.2: High-Speed CAN (125 kBit/s , 500 kBit/s)
1.1.3.1. Low-Speed CAN (83,3 kBit/s)
General CAN fundamentals
