Case IH 144 – Engine Control Module (ECM / ENG): Coolant Temperature Sensor voltage is too high

The engine controller has detected an abnormally high voltage signal at the coolant temperature signal pin 2 of the sensor harness connector. This almost always points to an open circuit or a short to a power source, which may result in white smoke and disabled engine protection features.

• MX Magnum
• STX Steiger
• Case IH MX Magnum Series (e.g., MX210, MX215, MX230, MX245, MX255, MX275, MX285, MX305)
• Case IH TG Series Tractors
• Steiger / Quadtrac Series (STX models)

1. 1

   Inspect the coolant temperature sensor and its wiring harness connector (specifically pin 2) for corrosion, backed-out pins, or physical damage.

2. 2

   Check the sensor signal wire between the sensor harness and the Engine Controller for an open circuit (broken wire) or a short to a 12V/5V power source.

3. 3

   Test the thermistor inside the sensor with a multimeter to verify if its internal resistance changes correctly with temperature or if it has failed open.

4. 4

   Check the sensor return/ground circuit to ensure it is intact, as a lost ground will cause the signal voltage to default to its maximum 5V reference.

1. 1

   Disconnect Power

   Disconnect the tractor's battery to prevent electrical shorts during repair.

2. 2

   Locate the Sensor

   Locate the engine coolant temperature sensor on the engine block (often near the thermostat housing or water pump).

3. 3

   Disconnect Harness

   Unplug the wiring harness from the sensor.

4. 4

   Repair Wiring (If Applicable)

   If the diagnostic checks revealed a broken wire or short in the harness, repair the wiring loom or replace the connector pigtail.

5. 5

   Replace Sensor (If Applicable)

   If the wiring is sound but the sensor is faulty, unscrew the old coolant temperature sensor from the engine block. Have a catch pan ready, as some coolant may leak out.

6. 6

   Install New Sensor

   Thread the new sensor into the block and tighten it to the manufacturer's torque specification.

7. 7

   Reassembly

   Reconnect the wiring harness to the new sensor.

8. 8

   Refill Coolant

   Top off the engine coolant to replace any fluid lost during the sensor swap.

9. 9

   Clear Codes

   Reconnect the battery, turn the key on, and use a diagnostic tool to clear the fault codes. Start the engine and verify that Code 144 does not return.