New Holland ENG 3900 – Engine Control Unit (ECU): Coolant Temp High: Engine temperature exceeded warning level

This code is triggered when the engine's coolant temperature surpasses the maximum safe operating threshold, prompting a critical warning to prevent severe engine damage.

• L220
• L223
• L225
• C227
• T4000 series
• TD5000 series
• TD5010
• TD5020
• Workmaster 75

1. 1

   Check the radiator and overflow tank to ensure the coolant is at the proper level

2. 2

   Inspect the radiator and cooling package for blockages caused by mud, chaff, or debris

3. 3

   Check the engine cooling fan and the drive belt for proper tension, slipping, or severe wear

4. 4

   Verify that the thermostat is opening at the correct temperature and not stuck closed

5. 5

   Inspect the coolant temperature sensor and its wiring harness for physical damage, corrosion, or a short/open circuit

1. 1

   Safety First

   Shut down the machine and allow the engine to cool completely. Never open a hot cooling system or remove a sensor while the system is pressurized.

2. 2

   Locate the Sensor

   Locate the engine coolant temperature sending unit. On F5C engines, this is typically located on the right side of the engine cylinder head or near the thermostat housing.

3. 3

   Disconnect Wiring

   Carefully unplug the electrical connector from the sensor.

4. 4

   Remove the Sensor

   Place a drain pan underneath the engine to catch any coolant that will escape. Unscrew and remove the faulty temperature sensor.

5. 5

   Install the New Sensor

   Thread the new OEM coolant temperature sensor into the port. (Note: If the new sensor does not have pre-applied thread sealant, apply a suitable liquid thread sealant to prevent leaks). Tighten to the manufacturer's torque specification.

6. 6

   Reconnect and Refill

   Reconnect the electrical harness to the new sensor. Top off the engine coolant to replace any fluid lost during the swap.

7. 7

   Test

   Start the engine and monitor the instrument cluster. Ensure the temperature gauge stays within the normal (grey) operating area and check the sensor port for leaks. Clear the ENG 3900 fault code using a diagnostic tool.