Case IH t4D – Powertrain Control Unit (PCU) / Engine Controller: Coolant Temperature Sensor, Data Valid But Above Normal Range

The sensor is functioning and sending a valid electrical signal to the controller, but the temperature reading is higher than the maximum normal operating threshold. This typically indicates that the engine is genuinely overheating, or the sensor's internal resistance has drifted, causing it to report a falsely high temperature.

• MXM
• MXM120
• MXM130
• MXM140
• MXM155
• MXM175
• MXM190

1. 1

   Check coolant levels: Ensure the radiator and coolant reservoir are filled to the proper level.

2. 2

   Inspect the cooling system: Look for physical cooling issues such as a blocked radiator/grille, a stuck-closed thermostat, a failing water pump, or a loose/broken fan belt.

3. 3

   Plausibility check: Compare the coolant temperature sensor reading to the engine oil temperature or ambient air temperature when the tractor is completely cold. If the coolant sensor reads significantly hotter than ambient temperature on a cold engine, the sensor is skewed.

4. 4

   Wiring inspection: Inspect the 2-terminal wiring harness and connector at the sensor for corrosion, moisture, or chafing, which can alter the resistance signal sent to the ECU.

1. 1

   Cool Down

   Allow the tractor engine to cool down completely to avoid burn injuries from hot, pressurized coolant.

2. 2

   Drain Coolant

   Drain a small amount of coolant from the radiator petcock to bring the fluid level below the sensor port. This prevents excessive coolant loss and spills during removal.

3. 3

   Disconnect Wiring

   Locate the coolant temperature sensor on the engine block/thermostat housing. Carefully depress the locking tab and disconnect the electrical wiring harness.

4. 4

   Remove Sensor

   Use a wrench to unscrew and remove the faulty coolant temperature sensor.

5. 5

   Install New Sensor

   Thread the new sensor into the port. Ensure the threads are clean and tighten to the manufacturer's specification (the MXM sensor typically uses an M17 x 1.50 metric thread).

6. 6

   Reconnect

   Plug the electrical harness connector back into the new sensor until it clicks securely.

7. 7

   Refill and Test

   Top off the engine coolant to the correct level. Start the engine, monitor the dashboard temperature gauge for accurate readings, and inspect the sensor area for leaks. Clear the fault code from the cluster if it does not clear automatically upon receiving a normal temperature reading.