Test 1: Engine compartment CAN test
1. Engine compartment CAN test
Test 1.1: Engine compartment CAN test
1.1. Engine compartment CAN test
Test 1.1.1: Procedure in case of CAN faults
Test 1.1.2: Read current CAN configuration and CAN fault codes
Test 1.1.3: Further CAN test options
1.1.1. Procedure in case of CAN faults
Test 1.1.1.1: Possible aids and their usage
Test 1.1.1.2: How do I quickly reach my goal?
Test 1.1.1.3: General test information
Test 1.1.1.4: General CAN fundamentals
1.1.1.1. Possible aids and their usage
Evaluation of CAN fault codes
- The control units present in the vehicle (actual configuration) are compared with the coding in control unit CGW (specified configuration).
- Filtering and evaluation of all CAN timeout fault codes present in the vehicleThe result of the evaluation leads to the required test steps.
Multimeter
- Aids for voltage and resistance measurement in menu item 'Measurements with multimeter on CAN network'
Measuring system
- Aid for graphic representation of CAN signal and voltage levels
- The specified characteristics shown in Measurement Technology are used to recognize changed CAN voltage levels, which can be caused by
faulty CAN components.
- Possible procedure: Disconnect and then reconnect the CAN bus subscribers at the voltage distributor one at a time.Compare the pass image
with the actual image from the oscilloscope.
Star Diagnosis CANtool
- Aids for representation of actual values and identification of bus wake-up events and bus keepawake events
Continue with button F2
1.1.1.1. No further information available.
1.1.1.2. 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.
1.1.1.3. 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
