Case IH t25 – Engine Control Unit (ECU): Boost Air Temperature Sensor, Data Valid But Above Normal Range

This code indicates that the engine's boost air temperature sensor is sending a valid electrical signal to the controller, but the temperature reading itself is higher than the acceptable normal operating threshold. This means the circuit is intact (not shorted or open), but the system is either detecting an actual overheating condition in the intake/boost air or the sensor's internal calibration has skewed, causing it to report falsely high temperatures.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190

1. 1

   Verify actual temperatures to ensure the turbocharger and intercooler are functioning correctly (check for restricted exhaust, plugged DPF, or blocked intercooler causing actual high boost temperatures)

2. 2

   Test sensor resistance with a multimeter and compare to OEM specifications (60°C = 595 ohms, 80°C = 322 ohms, 100°C = 186 ohms, 120°C = 112 ohms)

3. 3

   Check the continuity of the engine wiring harness between the ECU connector and the sensor connector

4. 4

   Verify the insulation of each wire to ensure there is no partial short to ground or power that might be skewing the voltage return

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent electrical spikes during the repair.

2. 2

   Locate the Sensor

   Locate the boost air temperature sensor. It is typically mounted on the intake manifold, after the intercooler, and before the Exhaust Gas Recirculation (EGR) valve.

3. 3

   Disconnect and Inspect

   Unplug the wiring harness from the sensor. Inspect the connector pins for corrosion, moisture, or damage.

4. 4

   Remove the Sensor

   Unthread the faulty boost air temperature sensor from its mounting port.

5. 5

   Install the New Sensor

   Thread the replacement sensor into the port and tighten to the manufacturer's torque specification.

6. 6

   Reconnect

   Plug the wiring harness back into the new sensor.

7. 7

   Clear Codes

   Reconnect the battery. Use a diagnostic scanner or the tractor's onboard H-Menu (Calibration/Configuration menu) to clear the t25 fault code.

8. 8

   Test Run

   Start the engine and monitor the boost air temperature data to ensure it remains within the normal operating range under load.