Absence of Hybrid battbus CAN communication (buffer overflow)
• Check connector for Hybrid Batt-bus on BMU(E81) pin A35 and A38. • Check wiring for Hybrid Batt-bus: - Measure the resistance on BMU(E81) (with the 24V battery disconnected) between CAN-high pin A35 and CAN-low pin A38. It should be close to 120ohm. - Measure the resistance on BMU(E81) (with the 24V battery disconnected) between CAN-high on BMU(E81) pin A35 and CAN-high on any other unit on the Hybrid batt-bus. It should be close to zero ohm. - Measure the resistance on BMU(E81) (with the 24V battery disconnected) between CAN-low on BMU(E81) pin A38 and CAN-low on any other unit on the Hybrid Batt-bus (Water pump(M38), Water pump(M41), IBU within battery pack (E83), and DCC(E84) . It should be close to zero ohm. • Check wiring and connector for the ignition signal pin B38 on the BMU(E81). • If no other errors can be found, change BMU(E81).
What you'll see
No driver-visible symptom recorded.
System reaction
• VOR, the hybrid system will not work since the battery will not be engaged. The DCC will not receive VCB-power and the 24-volt system will drain the 24-volt batteries. • Amber warning lamp "24V batteries not charged" and "Hybrid System Fault" is shown in ICL
Diagnostic depth
The fault is validated as present if the ECU tries to send CAN-messages on the Hybrid batt-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 Hybrid batt-bus (separate DTC)
• Defect connectors on ECUs in the RES. • Defect wiring for Hybrid Batt-bus, open circuit on CAN-high (pin B11) or CAN-low (pin B14). • Ignition signal (pin B38) on BMU(E81) is short circuit to supply.