CE4 BUS-OFF state of the system bus (CAN)

What does x065 mean?

The system bus (CAN) has entered a BUS-OFF state due to an excessive number of faulty telegrams. This indicates a severe and persistent communication problem on the CAN network, which is configured via parameter C0595.

• Persistent electrical noise or reflections on the CAN bus causing a high rate of bit errors and retransmissions.
• One or more nodes on the CAN bus are faulty, constantly transmitting erroneous data or acting as a 'babbling idiot'.
• Incorrect or missing termination resistors on the CAN bus, leading to severe signal integrity issues.
• Grounding problems creating voltage potential differences between CAN nodes, interfering with signal integrity.
• Severe physical damage to the CAN bus cable (e.g., short circuit between CAN_H and CAN_L, or to ground).

Click steps to track your progress.

1. 1

   1. Power down the drive, measure resistance across CAN_H and CAN_L terminals at both ends of the CAN bus; it should be 60 Ohms with two 120 Ohm terminators.

2. 2

   2. Use a CAN bus analyzer to identify the source of erroneous telegrams by monitoring error frames and bus load.

3. 3

   3. Isolate potential faulty nodes by disconnecting devices one by one and monitoring the bus status until the BUS-OFF state clears.

4. 4

   4. Check all CAN bus cable shielding for proper connection to ground at both ends, and ensure cables are routed away from noise sources.

5. 5

   5. Verify the internal parameter C065 (CAN Bus-Off Threshold) and consider adjusting it temporarily for diagnostic purposes, with caution.