Description

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

CAN ´bus off´ condition occurs if the fault counter of a CAN controller exceeds 255.

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

Driving is not possible or restricted.

Transmission shifts sporadically to neutral.

Lighting of the gear range selector becomes dark.

Possible causes

Short-circuit between CAN-H and CAN-L or short-circuit of one or both lines to ground or to supply voltage.

Another CAN bus party sends with an incorrect bit rate (250kbit/s are expected).

Other bus party is defective.

Defective CAN transceiver pushbutton control unit

Defective CAN transceiver in E330.

Place of action

No description available.

Instruction

Check the cabling (cable break, loose contact, high contact resistance).

Measure between CAN-H and CAN-L: the resistance must be approx. 60 ohms - install / repair bus terminating resistor if necessary.

Measure resistance between CAN-H and CAN-L (resistance must be about 60 ohms). Check/repair cabling if necessary.

Measure CAN-H and CAN-L to ground: The resistance must be significantly larger than 1kohm - check / repair cabling if necessary.

Measure CAN-H and CAN-L to supply voltage: The resistance must be significantly larger than 1kohm - check / repair cabling if necessary.

Check whether the correct dataset in the control unit (correct CAN protocol), if not, change dataset,

unplug other bus parties and check whether the fault is eliminated - replace defective control unit and/or contact with the manufacturer.

Unplug bus parties one after another and check whether the fault has been eliminated. Replace defective / faulted control unit. Replace gear range selector 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.