BMU5 Electrical error on Hybrid batt-bus (BusOff)
• Measure the resistance on E81 (with the 24V battery disconnected) between CAN-high pin B11 and CAN-low (pin B14). It should be close to 120 ohm. • Measure the resistance on E81 (with the 24V battery disconnected) between CAN-high pin B11 and supply. It should be high ohmic (Mega ohm). • Measure the resistance on E81 (with the 24V battery disconnected) between CAN-high pin B11 and ground. It should be high ohmic (Mega ohm). • Measure the resistance on E81 (with the 24V battery disconnected) between CAN-low pin B14 and supply. It should be high ohmic (Mega ohm). • Measure the resistance on E81 (with the 24V battery disconnected) between CAN-low pin B14 and ground. It should be high ohmic (Mega ohm). • Disconnect one ECU unit at the time (IBU within battery pack (E83), Water pump(M38), Water pump(M41) and DCC(E84) from the Hybrid Batt-bus and check if the fault disappears. • Change the faulty component NOTE! Replacing the IBU is considered an electrical work and shall only be performed by Scania certified personnel. Vehicle shall be made safe according to electrical work procedure.
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 DTC is set to active if CAN controller of the hybrid batt-bus is in the state bus-off. The DTC is set to inactive if the CAN-controller is not in state bus-off for 1100 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
• Defect wiring of hybrid batt-bus: - short circuit between CAN-high and CAN low. - short circuit between CAN-high and supply voltage. - short circuit between CAN-high and ground. - short circuit between CAN-low and supply voltage. - short circuit between CAN-low and ground. • Defect ECU unit(s) on the Hybrid Batt-bus.