BMU5 Electrical error on TMS sub-bus (BusOff)
• Measure the resistance on the connector to E81 (with the 24V battery disconnected) between CAN-high (pin B5) and CAN-low (pin B8). It should be close to 60 ohm (one 120 ohm termination resistor in each end of the CAN-bus). • Measure the resistance on the connector to E81 (with the 24V battery disconnected) between CAN-high (pin B5) and supply (pin A4). It should be high ohmic (Mega ohm). • Measure the resistance on the connector to E81 (with the 24V battery disconnected) between CAN-high (pin B5) and ground (pin A2). It should be high ohmic (Mega ohm). • Measure the resistance on the connector to E81 (with the 24V battery disconnected) between CAN-low (pin B8) and supply (pin A4). It should be high ohmic (Mega ohm). • Measure the resistance on the connector toE81 (with the 24V battery disconnected) between CAN-low (pin B8) and ground (pin A2). It should be high ohmic (Mega ohm). • Disconnect one ECU unit at the time from the TMS sub-bus and check if the fault disappears.
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 TMS sub-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 TMS sub-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 TMS sub-bus.