Case IH P28 – Engine Control Unit (ECU): Boost Air Temperature Sensor (PHY), Data Valid But Above Normal Range

While Code P28 is officially listed as 'Not used', the provided description corresponds to Fault Code T28 (105-0). It indicates that the Boost Air Temperature Sensor is functioning and sending a valid electrical signal, but the temperature reading is higher than the acceptable threshold, meaning the system believes the engine is genuinely experiencing an overheating condition in the intake air.

• MXM
• MXM Series (MXM 120, 130, 140, 155, 175, 190)
• Puma
• Magnum
• Steiger

1. 1

   Inspect the charge air cooler (intercooler) and radiator for blockages from dirt, chaff, or debris restricting airflow.

2. 2

   Check the engine cooling fan (viscous drive or electronic fan clutch) to ensure it is engaging properly when the engine gets hot.

3. 3

   Test the Boost Air Temperature Sensor resistance with a multimeter to see if it has drifted out of specification (Typical EDC7 values: 60°C = 595 ohms, 80°C = 322 ohms, 100°C = 186 ohms, 120°C = 112 ohms).

4. 4

   Inspect the turbocharger for signs of failure, which can generate excessive heat and push intake air temperatures above normal limits.

1. 1

   Cool engine

   Turn off the tractor, remove the key, and allow the engine to cool completely.

2. 2

   Locate sensor

   Locate the Boost Air Temperature Sensor. It is threaded into the intake manifold, downstream of the charge air cooler (intercooler).

3. 3

   Disconnect harness

   Depress the locking tab and disconnect the electrical wiring harness from the sensor.

4. 4

   Remove old sensor

   Using a deep socket or wrench, carefully unthread the old sensor from the intake manifold.

5. 5

   Install new sensor

   Thread the new sensor into the manifold by hand to prevent cross-threading, then tighten to the OEM torque specification (do not overtighten, as the manifold threads can strip).

6. 6

   Reconnect harness

   Reconnect the electrical harness until it clicks.

7. 7

   Clear fault code

   Turn the key to the 'ON' position and use the tractor's H-Menu or a diagnostic scan tool to clear the stored T28 / 105-0 fault code.

8. 8

   Verify repair

   Start the engine and run it under load to verify the code does not return.