Description

Communication on the CAN bus fails due to CAN ´bus off´ conditions.

'bus off' : If the fault counter of a CAN controller exceeds the value 255, the CAN-controller will assume the 'bus off' status. The CAN controller is disconnected from the CAN bus using an internal logic function and does no longer participate in the bus activities. The control unit that belongs to the CAN controller can no longer receive or send CAN messages.

Effects on the driving operation

No CAN-communication via the CAN-controller 1 of the transmission control unit possible.

Driving is not possible or restricted.

Possible causes

Short-circuit between CAN-H and CAN-L or short-circuit of a CAN-cable to ground.

- A bus party is sending with incorrect bit rate.

- Another defective control unit is connected to the CAN bus

- Defective CAN transceiver pushbutton control unit

Place of action

No description available.

Instruction

Measure resistance between CAN-H and CAN-L ( ~ 60 Ohm ).

Check cabling.

- Measure resistance between CAN-H and CAN-L to ground: The resistance must lie well above 1 kOhm.

- Check whether the correct dataset and correct CAN protocol are active.

- Disconnect all control units from the CAN bus one after the other and check whether this eliminates the fault.

- Replace transmission control unit.

Setting conditions of the event

No description available.

Testing conditions of the event

No description available.

Final function check

If the defective component cannot be clearly identified, you should try to reproduce the fault:

• Reinstall the component in the vehicle.
• Test function.

After the fault has been eliminated, the following steps have to be carried out:

• Conduct a test drive with function check.
• Read the fault memory
• Check transmission for leaks.
• Perform a final visual inspection.

These steps are necessary to ensure the entire vehicle functions correctly.