New Holland 144 – ENGINE (ECM/ECU): Coolant Temperature Sensor Voltage Is Too High

The Engine Control Module (ECM) has detected that the voltage signal from the engine coolant temperature sensor is above the normal operating range, typically greater than 5.13-VDC. This condition indicates an open circuit, a short to a voltage source in the wiring, or a failed sensor. Because the ECM relies on accurate coolant temperature data for fuel injection timing and engine protection, it may default to a pre-set temperature value when this fault is active. This can result in symptoms such as white exhaust smoke, the engine cooling fan running continuously, and a loss of proper engine protection against overheating.

• T4
• T5
• T8
• T9
• TM120
• TM130
• TM140
• TM155
• TM175
• TM190
• TJ
• T8.275
• T8.300
• CR9040
• CR9060
• AFX8010
• L185
• L225
• L230
• U80C

1. 1

   Check for multiple active fault codes, as the coolant temperature sensor may share a return wire with other sensors; an open shared return circuit can trigger several faults simultaneously.

2. 2

   Inspect the coolant level and condition to ensure there are no air pockets in the system affecting the sensor's reading.

3. 3

   Visually inspect the coolant temperature sensor's electrical connector and wiring harness for signs of damage, corrosion, or loose connections.

4. 4

   Perform a wiring harness check (key ON, sensor disconnected): measure voltage between the sensor wire terminal in the harness and chassis ground. Expect approximately 5V (or battery voltage). 0V indicates an open circuit, while significantly higher than 5V indicates a short to power.

5. 5

   Perform a sensor resistance test (sensor disconnected): measure resistance between the sensor's electrical pin and its body. Expect approximately 4300 Ohms at 60°F (15°C) and 180 Ohms at 212°F (100°C). Infinite resistance indicates a failed sensor.

1. 1

   Prepare machine

   Ensure the engine is completely cool to prevent burns. Park the vehicle on a level surface and disconnect the negative battery cable.

2. 2

   Relieve cooling system pressure

   Briefly open the radiator or coolant reservoir cap to release any residual pressure, then retighten it to minimize coolant loss.

3. 3

   Remove faulty sensor

   Locate the sensor on the engine block (often near the thermostat housing). Disconnect the electrical connector by releasing the locking tab, place a drain pan underneath, and unscrew the old sensor using a deep socket or wrench.

4. 4

   Install new sensor

   Install the new sensor using a new sealing washer or thread sealant if specified. Hand-thread into place to avoid cross-threading, then tighten snugly. Do not overtighten. Reconnect the electrical connector securely.

5. 5

   Finalize repair

   Top off the cooling system with the correct fresh coolant. Reconnect the negative battery cable, start the engine, check for leaks, allow the engine to reach operating temperature, and use a diagnostic tool to clear fault code 144 from the ECM.