New Holland ENG 151 – ENGINE Controller (Engine ECU): Coolant Temperature level has exceeded the warning limit

The engine is either actively overheating due to a mechanical/cooling system failure, or the coolant temperature sensor is sending a faulty, out-of-range high-temperature reading to the system.

• New Holland T4
• New Holland T5
• New Holland T6
• New Holland T7
• New Holland T8
• New Holland T9
• New Holland TM Series (TM120-TM190)
• New Holland Workmaster
• New Holland CX Series (CX8080)
• New Holland CR Series (CR9060)
• New Holland skid steers
• New Holland backhoe loaders
• New Holland wheel loaders

1. 1

   Safety First: Never open the radiator cap while the engine is hot. Wait 30 to 45 minutes for the engine to cool down.

2. 2

   Inspect Airflow (Most Common Cause): Check the radiator stack and front screens for blockages caused by dirt, dust, or agricultural chaff. Blow out the radiator thoroughly. Verify the fan clutch, belt condition, and shrouds.

3. 3

   Check Coolant System: Verify the coolant fluid level in the overflow tank and radiator. Inspect for collapsed hoses, leaks, and ensure the pressure cap is functioning.

4. 4

   Verify Coolant Flow: Check the water pump performance and the temperature spread across the radiator to ensure the thermostat is opening and fluid is circulating.

5. 5

   Check Hydraulic Drag: Ensure no hydraulic components are running constantly on relief, which can overload the engine and cause overheating.

6. 6

   Sensor & Wiring Check: If the engine is physically cool but the gauge reads hot (or is erratic), inspect the coolant temperature sensor's wiring harness and ground points for loose connections, corrosion, or shorts.

1. 1

   Cool Down

   Ensure the engine is completely cool and the cooling system is depressurized.

2. 2

   Locate the Sensor

   Find the coolant temperature sensor, which is typically positioned directly on the engine thermostat housing or the cylinder head water jacket tract.

3. 3

   Disconnect Wiring

   Unplug the 2-pin wiring harness connector from the sensor.

4. 4

   Remove the Sensor

   Unthread the faulty sensor from the engine's coolant passage (many use a standard 1/2" x 14 NPTF metric thread). Have a catch pan ready for any minor coolant spillage.

5. 5

   Install the New Sensor

   Thread the new OEM sensor into the housing and tighten to the manufacturer's specification.

6. 6

   Reconnect and Refill

   Plug the wiring harness back in. Top off the engine coolant to replace any fluid lost during the swap.

7. 7

   Clear Codes and Test

   Clear the ENG 151 fault code from the Engine ECU using a diagnostic tool. Run the tractor under load to verify that the temperature gauge reads accurately and the code does not return.