Communication error on HCU CAN bus. CAN-bus buffer overflow.
• Check connector for HCU CAN-bus on ACUB1 (pin B1 and B10). • Check wiring for CAN-bus: - Measure the resistance (with the battery disconnected) between CAN-high (pin B1) and CAN-low (pin B10). It should be close to 60 ohm (one 120 ohm termination resistor in each end of the CAN-bus). - Measure the resistance (with the battery disconnected) between CAN-high on ACUB1 (pin B1) and CAN-high on any other unit on the expansion CAN-bus. It should be close to zero ohm. - Measure the resistance (with the battery disconnected) between CAN-low on ACUB1 (pin B10) and CAN-low on any other unit on the expansion CAN-bus. It should be close to zero ohm.
What you'll see
No driver-visible symptom recorded.
System reaction
• Functions dependent on information on the HCU CAN bus from ACUB1 might be degraded. Examples listed below. - Secondary braking not working (EPB) - Degraded autonomous function
Diagnostic depth
The fault is validated as present if the ECU tries to send CAN-messages on the HCU CAN bus, but no acknowledge is received from other units, and thereby causing the internal send buffer (in the ECU) to overflow. The DTC is set to active if the buffer overflow has lasted for 50 ms. The DTC is set to inactive when the CAN-messages are sent properly again and the buffer no longer is overflowing for the last 1050 ms. The DTC is not validated (stored) if: • the ignition is turned off • first 2 seconds after ignition on • the supply voltage is below 22 volt • the supply voltage is above 32 volt • short circuit on expansion CAN-bus (separate DTC)
• Defect connectors on ACUB1 for HCU CAN bus (pin B1 or B10). • Defect wiring for CAN-bus, open circuit on CAN-high (pin B1) or CAN-low (pin B10).