New Holland ENG 3577 – Engine Control Unit (EDC / Engine ECU): DM1DCU SPN1 message - Error in DCU active

The Engine Control Unit has received a CAN bus message from the Dosing Control Unit (DCU) stating that there is an active internal error within the DCU.

• T7 Series Tractors (T7.185, T7.270)
• T8 Series Tractors
• CR and CX Series Combines (CR9090, CX8080, CX8090)
• Compact Track Loaders and Skid Steers (C227, L228)

1. 1

   Connect the CNH Electronic Service Tool (EST) to read specific internal fault codes stored directly in the DCU

2. 2

   Check for accompanying CAN timeout codes (such as 3537) that indicate wiring failure or loss of communication rather than an internal DCU hardware fault

3. 3

   Inspect the CAN bus wiring harness, connectors, and pins between the Engine ECU and the Denox Supply Module/DCU for corrosion or damage

4. 4

   Verify that the DCU is receiving proper supply voltage and ground, and check the DEF system fuses

1. 1

   Diagnose via EST

   Use the CNH EST diagnostic tool to pinpoint the exact component failure within the SCR/DEF system based on the DCU's internal codes.

2. 2

   Harness Repair

   If wiring damage is found during the diagnostic checks, repair the CAN lines or power/ground circuits leading to the DCU.

3. 3

   Software Update

   If the wiring is intact, check if there is a software malfunction. Reprogramming or flashing the controller may resolve the issue without replacing hardware.

4. 4

   Module Replacement

   If the module has failed electronically, replace the Dosing Control Unit (often integrated into the Denox supply module).

5. 5

   Programming

   Install the new DCU. CNH requires software installation and calibration when replacing this module. You will need the CNH EST tool, and CNH will not issue programming passwords unless official troubleshooting steps have been documented.

6. 6

   System Test

   Clear all fault codes and perform an SCR system test or test drive to verify the repair.