New Holland ENG 3555 – Engine Control Unit (ECU / EDC): CAN Message timeout SCR2 (from DCU) - CAN timeout

The Engine Control Module has lost communication over the Controller Area Network (CAN) bus with the Dosing Control Unit (DCU). Specifically, the engine controller is no longer receiving the expected "SCR2" data message from the DCU, which is responsible for managing the Selective Catalytic Reduction (SCR) system and DEF/AdBlue injection.

• New Holland T7 Series (T7.220, T7.235, T7.250, T7.260, T7.270)
• New Holland T8.xxx Series
• New Holland CR9090 Combine
• New Holland CX8080 Elevation Combine
• New Holland CX8090 Elevation Tier 4A Combine

1. 1

   Check for programming overlap: If a software update was just performed, ignore the code, clear the fault codes from the ECU and DCU modules, and retest the system.

2. 2

   Check for multiple CAN faults: Look for other CAN timeout codes (e.g., 3537, 3541). If multiple modules are dropping offline, there may be a broader CAN bus short or network issue.

3. 3

   Verify DCU power supply: Check for undervoltage or missing power to the DCU. Inspect the fuses and relays supplying the DCU.

4. 4

   Inspect the CAN harness: Check the CAN cable connecting the DCU to the network. Look for disconnected plugs, broken wires, or short circuits in the wiring.

1. 1

   Verify the Fault

   Connect the CNH Electronic Service Tool (EST) to verify if the fault is currently active.

2. 2

   Inspect Wiring and Connectors

   Turn off the machine and disconnect the battery. Visually inspect the wiring harness between the Engine ECU and the DCU. Look for chafed wires, moisture intrusion, corrosion, or pushed-back pins at the connectors.

3. 3

   Test Power and Ground

   Measure the voltage at the DCU connector to ensure it is receiving proper battery voltage and has a solid ground. Repair any blown fuses or damaged power supply wires.

4. 4

   Test CAN Bus Integrity

   Measure the resistance across the CAN High and CAN Low pins at the DCU connector (with batteries disconnected). Check for open circuits or shorts to ground/power on the CAN lines.

5. 5

   Replace the DCU

   If the wiring, power, and ground are all verified as good, but the DCU still fails to communicate on the CAN bus, the DCU itself has an internal CAN controller failure and must be replaced.

6. 6

   Programming

   If the DCU is replaced, the new module requires software installation and initialization using the CNH diagnostic tool before it will function.