Kubota P3025 – Engine ECU (Engine Control Unit): Over heat pre-caution

Triggered when the engine coolant temperature reaches 110°C (230°F) or higher. The ECU sets this code under the specific precondition that the coolant temperature sensor is functioning normally, indicating a true engine overheating event. When active, the ECU may inhibit DPF regeneration, limit engine output, and log worsening exhaust gas emissions (NOx).

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1. 1

   Ensure the engine is completely cool, then check the radiator and overflow tank for proper coolant levels and signs of external leaks.

2. 2

   Inspect the radiator fins for blockages caused by dirt, chaff, or debris (a very common cause of overheating in agricultural environments).

3. 3

   Inspect the cooling fan for damage and check the fan belt for proper tension and signs of wear or slipping.

4. 4

   Verify thermostat operation by checking if the upper radiator hose gets hot once the engine reaches operating temperature. If it remains cold while the engine overheats, the thermostat is likely stuck closed.

5. 5

   Use Kubota Diagmaster software or a multimeter to verify the coolant temperature sensor's resistance curve matches the actual coolant temperature.

1. 1

   Cool Down

   Safely shut down the machine and allow the engine to cool completely to avoid severe burns.

2. 2

   Clean & Top Off

   Blow out the radiator fins with compressed air. Top off the coolant using Kubota-approved coolant (e.g., 50/50 mix).

3. 3

   Belt Adjustment

   If the fan belt is loose, adjust the alternator/tensioner bracket to achieve the correct belt deflection, or replace the belt if it is glazed or cracked.

4. 4

   Thermostat Replacement

   If overheating persists: Drain the coolant from the radiator petcock. Remove the upper radiator hose from the thermostat housing. Unbolt the thermostat housing and remove the old thermostat and gasket. Clean the mating surfaces, install the new thermostat (jiggle valve facing up, if applicable), and install a new gasket. Re-torque the housing bolts to OEM spec.

5. 5

   Sensor Replacement

   If sensor is reading falsely high: Locate the coolant temperature sensor on the engine block/cylinder head. Disconnect the wiring harness. Unthread the old sensor and quickly thread in the new one to minimize coolant loss. Tighten securely.

6. 6

   Refill & Bleed

   Refill the cooling system. Leave the radiator cap off, start the engine, and let it idle to bleed trapped air from the system. Top off as the level drops.

7. 7

   Clear Codes

   Use the Kubota Diagmaster tool to clear the P3025 code (or cycle the key switch, as the diagnostic counter often resets to zero once the error is resolved). Test the machine under load to ensure the temperature holds steady.