Scania BMU DTC 544 Timeout in direct current converter E84 (DCC) CAN node

BMU Battery Management Unit · Scania · 2 variants

Code 544 (decimal). Some diagnostic tools show it in hexadecimal as 0220.

In short

Communication with the direct current converter interrupted. The fault code becomes inactive when the direct current converter CAN message is received.

Variant 1

Applies to: BMU6 (RES)BMU6 (RESXA)BMU6 (RESXB)BMU6 (RESXC)BMU6 (RESXD)BMU6 (RESXE)BMU6 (RESXF)BMU6 (RESXG)BMU6 (RESXH)BMU6 (RESXI)BMU6 (RESXJ)BMU6 (RESXK)

What does Scania BMU fault code 544 mean?

Communication with the direct current converter interrupted. The fault code becomes inactive when the direct current converter CAN message is received.

What causes Scania DTC 544?

Electric power supply to direct current converter missing. The direct current converter is disconnected from RES-CAN. Faulty direct current converter.

How does the system react?

Yellow warning indication of a system malfunction is displayed.

What are the symptoms?

If the vehicle has multiple propulsion batteries: - The contactors cannot be closed on the relevant propulsion battery. - The vehicle's total battery capacity and range are reduced. If the vehicle has only one propulsion battery: - VOR. - Electric drive of the vehicle is not possible. - The vehicle's 24 V voltage is turned off. - No charge is possible.

How to fix Scania BMU fault code 544?

  1. Check the fault codes in BMU E81.
  2. Check the following if no fault codes can be found in BMU:
  3. Electric power supply for 15 voltage to DCC.
  4. Check the cable harness and harness-to-component connectors for RES SUB CAN.

Variant 2

Applies to: BMU5

Detection

Communication with the direct current converter interrupted. The fault code becomes active if the direct current converter CAN message has been missing for 200 ms. The fault code becomes inactive when the direct current converter CAN message is received. The fault code is not set in the following scenarios: - if 15 voltage is off. - during the first 2 seconds after the 15 voltage has been switched on. - if the supply voltage is below 22 V. - if the supply voltage is above 32 V. - in the event of a short circuit or open circuit on RES-CAN (separate fault code).

Possible cause

Electric power supply to direct current converter missing. The direct current converter is disconnected from RES-CAN. Faulty direct current converter.

System reaction

Yellow warning indication of a system malfunction is displayed.

Symptoms

Risk of VOR. Direct current converter E84 (DCC) does not generate 24 V which will drain the 24 V batteries.

How to fix

  1. Check the fault codes in BMU E81.
  2. Check the following if no fault codes are found in the BMU:
  3. Electric power supply (pin A4) and signal for the 15 voltage (pin A1) on the BMU.
  4. Electric power supply (pin A3) and signal for the 15 voltage (pin A7) on the direct current converter.
  5. The CAN connection to the direct current converter on CAN-high (pin 1) and CAN-low (pin 2).
  6. Cable routing and harness-to-component connectors for RES-CAN.
  7. Disconnect the 24 V battery and measure the resistance between CAN-high (pin B11) and CAN-low (pin B14).
  8. The value should be close to 60 ohms (a 120 ohm resistor is located at each end of the CAN bus).

This information is for guidance only. Always follow the manufacturer workshop manual and safety procedures; if in doubt, contact an authorised workshop.

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