Scania BMU DTC 561 CAN communication for RES-SUB-CAN missing

BMU Battery Management Unit · Scania · 2 variants

Code 561 (decimal). Some diagnostic tools show it in hexadecimal as 0231.

In short

Communication error. RES-SUB-CAN has an open circuit.

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 561 mean?

Communication error. RES-SUB-CAN has an open circuit.

What causes Scania DTC 561?

Fault in the cable harness or harness-to-harness connectors. The 15 voltage signal on BMU E81 is missing.

How does the system react?

Yellow warning indication of an electric drive system fault is displayed.

What are the symptoms?

Risk of VOR. The electric drive system stops working because the propulsion battery is not available. Direct current converter E84 (DCC) is not supplied with voltage class B and the 24 V system will drain the 24 V batteries.

How to fix Scania BMU fault code 561?

  1. Check the cable routing of RES SUB CAN:
  2. Disconnect the 24 V battery and measure the resistance on BMU between CAN high and CAN low.
  3. The value should be close to 120 ohms.
  4. Disconnect the 24 V battery and measure the resistance on BMU between CAN high and CAN high on another unit on RES-SUB-CAN.
  5. The value should be close to 0 ohms.
  6. Disconnect the 24 V battery and measure the resistance on BMU between CAN low and CAN low on another unit on RES-SUB-CAN.
  7. The value should be close to 0 ohms.
  8. Check the cable routing and harness-to-component connectors for the 15 voltage signal for BMU.

Variant 2: CAN communication for RES-CAN missing

Applies to: BMU5

Detection

Communication error. Buffer for RES-CAN overfull. RES-CAN has an open circuit. The fault is detected if the control unit tries to send CAN messages on RES-CAN and it does not receive any acknowledgement from other units. It causes the internal transmission buffer to become overfull. The fault code becomes active if the buffer is overfull for more than 50 ms. The fault code becomes inactive when CAN messages are sent correctly and the buffer has not been overfull for the last 1,050 ms. The fault code is not stored: - If the 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 on RES-CAN (separate fault code).

Possible cause

Defective harness-to-component connectors on RES control units. Incorrect cable routing for RES-CAN. Open circuit on CAN-high (pin B11) or CAN-low (pin B14). The signal for the 15 voltage (pin 1) on BMU E81 has been short-circuited.

System reaction

Yellow warning indication of an electric drive system fault is displayed.

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

  1. Check the harness-to-component connectors for RES-CAN on the BMU.
  2. Check the cable routing for RES-CAN:
  3. Disconnect the 24 V battery and measure the resistance on BMU between CAN-high (pin B11) and CAN-low (pin B14).
  4. The value should be close to 120 ohms.
  5. Disconnect the 24 V battery and measure the resistance on the BMU between CAN-high (pin B11) and CAN-high on another unit on RES-CAN.
  6. The value should be close to 0 ohms.
  7. Disconnect the 24 V battery and measure the resistance on the BMU between CAN-low (pin B14) and CAN-low on another unit on RES-CAN.
  8. The value should be close to 0 ohms.
  9. Check the cable routing and harness-to-component connectors for the 15 voltage signal (pin A1) on the BMU.

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

Code 561 in other Scania systems

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