New Holland DCU 19606 – DCU (Dosing Control Unit): CAN receive frame ET1 (Oil and Water temp engine) | too many CAN messages | P0600 Serial Communication Link

This is a Controller Area Network (CAN) bus communication error. The Dosing Control Unit (DCU) is receiving an abnormally high number of messages (or corrupted data interpreted as too many messages) regarding the 'ET1' data frame, which carries the engine oil and water temperature data from the Engine Control Module (ECM). This triggers a P0600 Serial Communication Link error, indicating a breakdown in the data network between the engine and the emissions system.

• New Holland T7 Series (T7.220, T7.235, T7.250, T7.260, T7.270)
• New Holland T8 Series
• New Holland T9 Series

1. 1

   Verify if the code is active or stored by clearing the code and operating the machine to see if it returns.

2. 2

   Check for accompanying CAN bus codes (e.g., 19605 timeout, 19607 out of range, or ECM-side codes). Multiple modules reporting P0600 errors indicate a physical CAN bus wiring problem rather than a failed DCU.

3. 3

   Inspect the wiring harness between the Engine ECU and the DCU for chafed wires, corrosion at the connectors, or pushed-out pins.

4. 4

   With the battery disconnected, measure the resistance across CAN High and CAN Low at the diagnostic port. It should read approximately 60 ohms. A reading of 120 ohms indicates a missing terminating resistor or an open circuit.

5. 5

   Check if there is a known software update for the DCU or Engine ECU, as communication timing issues are frequently resolved via OEM software flashes.

1. 1

   Disconnect power

   Turn off the battery disconnect switch to prevent electrical spikes before beginning any physical repairs.

2. 2

   Repair wiring harness

   If diagnostic checks revealed damaged CAN wiring or corroded pins at the DCU connector, repair the wiring harness or replace the damaged connector pins.

3. 3

   Update software

   If the wiring is intact, connect the OEM diagnostic tool (e.g., CNH Electronic Service Tool) and flash the DCU and Engine ECU to the latest software calibration.

4. 4

   Replace Dosing Control Unit (DCU)

   If the wiring is verified good, the software is up to date, and the DCU continues to fail to process the ET1 CAN frame properly, the DCU hardware has failed internally and must be replaced.

5. 5

   Program new DCU

   The new DCU module will be blank. It must be programmed with the CNH EST tool to match the tractor's specific emissions configuration.