New Holland 3537 – ECU: CAN Message Timeout from DCU

Fault code 3537 is logged by the Engine Control Unit (ECU) when it fails to receive expected data messages from the Dosing Control Unit (DCU) over the CAN bus network. The DCU manages the injection of Diesel Exhaust Fluid (DEF) for the Selective Catalytic Reduction (SCR) emissions system. A communication timeout indicates a disruption in the data link, which can force the engine into a reduced power limp mode to maintain emissions compliance and prevent system damage. A master warning light may also be active on the instrument cluster.

• T7.210
• T7.220
• T7.230
• T7.245
• T7.260
• T7.270
• 5130
• 6130
• 7130
• 7230
• 8230
• 9230
• 450
• 500
• 550
• 600

1. 1

   Review all active fault codes using a diagnostic service tool for errors related to NOx sensors, the CAN bus network, or power supply

2. 2

   Inspect Diesel Exhaust Fluid (DEF) quality for contamination, dilution, or age, and look for crystallization around the tank or injector

3. 3

   Identify the DCU's location (e.g., under engine access steps on CR combines or near the hydraulic reservoir on related Case IH models) as the first step to checking its connections

4. 4

   Visually inspect the wiring harness and connectors between the ECU and DCU for abrasion, melting from exhaust heat, corrosion, or bent pins, and ensure they are securely seated

5. 5

   Perform a CAN bus electrical health check with power off by measuring termination resistance across CAN High and CAN Low (approximately 60 ohms is normal; 120 ohms suggests a missing terminating resistor, while lower values indicate a short circuit or faulty module)

6. 6

   Check CAN bus voltage levels with power on (CAN High should be ~2.5-3.0V, CAN Low should be ~2.0-2.5V); deviations can point to a short or a malfunctioning electronic module dragging the network down

1. 1

   Resolve prerequisite faults

   Diagnose and repair any other active fault codes related to the CAN bus, power supply, or NOx sensors before proceeding.

2. 2

   Repair harness and connections

   Repair or replace any damaged wiring or connectors found during inspection. Ensure all connections are clean, tight, and free of corrosion.

3. 3

   Verify DCU power and ground

   Confirm that the Dosing Control Unit is receiving the correct voltage and has a solid connection to ground. A loss of either will take the module offline.

4. 4

   Isolate the DCU module

   Temporarily disconnect the DCU from the CAN network. If communication between other modules on the network is restored, the DCU is likely the source of the fault.

5. 5

   Replace the Dosing Control Unit

   If the DCU is identified as faulty, replace it. A new DCU requires software installation and calibration using the official New Holland Electronic Service Tool (EST). Note that CNH may not provide the required software passwords unless proper troubleshooting has been documented.

6. 6

   Clear codes and verify repair

   Use a diagnostic tool to clear fault code 3537. Operate the machine through a full drive cycle to allow the ECU to confirm the repair and ensure the fault does not reappear.