Case IH 145 – Engine Controller (ENG) / Engine ECU: Coolant Temperature Sensor voltage is too low

This code indicates that the voltage signal returning from the Engine Coolant Temperature Sensor to the control module has dropped below the acceptable operating threshold. Technically, this usually points to a short to ground in the sensor circuit, a damaged wiring harness, or an internally shorted/failed sensor.

• MX Magnum
• STX Steiger
• MX Magnum Series
• TG Series
• Puma Series
• Maxxum Series
• Steiger Series

1. 1

   Inspect the wiring between the Coolant Temperature Sensor and the Engine ECU for chafed wires, melted insulation, or pinched lines that could cause a short to ground.

2. 2

   Disconnect the sensor and check the electrical connector for corrosion, moisture, or bent pins, which can disrupt the voltage signal.

3. 3

   Use a multimeter to test the sensor's resistance and voltage. If it is internally shorted, it will pull the reference voltage down.

4. 4

   Ensure the radiator is full and the system is free of air pockets, as an unsubmerged sensor can sometimes cause erratic readings.

1. 1

   Prep the Machine

   Park the tractor on hard, level ground. Turn off the engine, apply the parking brake, remove the key, and allow the engine to cool completely.

2. 2

   Drain Coolant

   Drain the engine coolant to a level just below the temperature sensor port to prevent spills during removal.

3. 3

   Disconnect the Sensor

   Unplug the electrical connector from the faulty coolant temperature sensor.

4. 4

   Remove the Sensor

   Unthread the old sensor from the engine block or coolant port.

5. 5

   Prepare the New Sensor

   Clean the threads on the engine port thoroughly. Apply a high-quality thread sealant to the threads of the new sensor (unless it comes with pre-applied sealant) to prevent leaks.

6. 6

   Install the New Sensor

   Thread the new sensor into the port and tighten it to the OEM torque specifications.

7. 7

   Reconnect Wiring

   Plug the electrical connector back into the sensor, ensuring it clicks securely into place.

8. 8

   Refill and Bleed

   Refill the cooling system with the correct specification coolant. Bleed the system to remove any trapped air pockets.

9. 9

   Test

   Start the engine and check for leaks around the new sensor. Verify that the temperature gauge on the dash is reading correctly and that Fault Code 145 has cleared from the Engine ECU.