New Holland 3009 – ECU: Coolant Temperature Signal - No Signal

The Engine Control Unit (ECU) has detected a complete loss of signal from the engine coolant temperature sensor. This prevents the system from properly monitoring engine temperature, which can lead to operational issues such as the engine entering a derated (limp mode) state or the cooling fan running continuously to prevent potential overheating.

• TM120
• TM130
• TM140
• TM155
• TM175
• TM190
• T8.275
• T8.300
• T4
• T5
• T9
• TJ
• MXM
• B90B
• B95
• B110
• U80C
• L180
• L185
• L190
• L225
• L230
• C185
• C190
• C232
• W110
• W130
• CR
• AFX

1. 1

   Check the engine coolant level to ensure it is correct; a low level can cause air pockets around the sensor, leading to incorrect readings or faults.

2. 2

   Visually inspect the wiring harness and connector leading to the coolant temperature sensor (typically located on the engine block near the thermostat housing or upper radiator hose) for damage, corrosion, dirt, or loose connections.

3. 3

   Test for voltage at the sensor connector: disconnect the harness, turn the key to the 'ON' position (engine off), and use a multimeter to check for voltage at the terminal. It should be close to battery voltage. No voltage indicates a wiring harness or ECU fault.

4. 4

   Test the sensor's resistance: connect a multimeter (set to Ohms) to the sensor's terminals. Resistance should be high when cold (around 2000 ohms) and decrease steadily as it warms up. A sensor can be bench-tested by removing it and placing it in hot water while monitoring the resistance change. An 'open circuit' (infinite resistance) or no change in resistance indicates a faulty sensor.

1. 1

   Disconnect battery

   Always disconnect the battery's negative terminal before beginning electrical repairs.

2. 2

   Drain coolant

   If necessary, drain a sufficient amount of coolant from the radiator to ensure the coolant level is below the sensor's position, preventing spills.

3. 3

   Remove the old sensor

   Disconnect the electrical connector from the sensor. Using a wrench, carefully unscrew and remove the old sensor from the engine block.

4. 4

   Install the new sensor

   Apply thread sealant to the new sensor's threads if it is not pre-applied. Install the new sensor and tighten it to the manufacturer's specified torque. Do not overtighten.

5. 5

   Reconnect and refill

   Reconnect the electrical connector to the new sensor. Refill the cooling system with the manufacturer-recommended coolant.

6. 6

   Bleed the system

   Bleed any air from the cooling system as per the machine's service manual to prevent air pockets.

7. 7

   Clear fault codes

   Reconnect the battery. Start the engine and use a diagnostic tool or the vehicle's onboard display to clear the active fault code.