Case IH P23 – EECU or VECU: Boost Air Temp Sensor Open Circuit

The control module has detected an open circuit or a current/voltage drop below the normal operating threshold in the Boost Air Temperature Sensor circuit. Note that standard documentation lists this specific sensor fault as code T23, while P23 designates a 4WD output open circuit. This NTC thermistor monitors intake/boost air temperature to manage exhaust gas recirculation and protect the engine. An open circuit typically indicates a broken wire, an unplugged connector, or a completely failed internal sensor element.

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

1. 1

   Locate the Boost Air Temperature Sensor and check the electrical connector to ensure it is fully seated and not unplugged.

2. 2

   Inspect the wiring harness between the sensor and the ECU for chafing, breaks, or melted insulation.

3. 3

   Disconnect the sensor and check for corroded, bent, or pushed-back pins inside the connector.

4. 4

   Measure the resistance across the sensor's terminals using a multimeter. Because it is an NTC thermistor, resistance should drop as temperature rises (e.g., roughly 595 ohms at 60°C, 322 ohms at 80°C, and 186 ohms at 100°C). If the multimeter reads 'OL' (open loop) or infinite resistance at ambient temperature, the sensor has failed internally.

1. 1

   Power down machine

   Turn off the tractor, remove the key, and allow the engine and charge air piping to cool to a safe temperature.

2. 2

   Disconnect sensor

   Unplug the electrical connector from the Boost Air Temperature Sensor.

3. 3

   Remove faulty sensor

   Using the appropriate deep socket or wrench, carefully unthread the faulty sensor from the intake manifold or boost piping.

4. 4

   Install new sensor

   Thread the new replacement sensor into the port and tighten to the manufacturer's specified torque without overtightening.

5. 5

   Reconnect harness

   Plug the electrical harness back into the sensor, ensuring the locking tab clicks into place.

6. 6

   Clear codes and test

   Turn the key to the ON position. Check the digital instrument cluster or diagnostic menu to verify that code T23 has moved from 'Active' to 'Inactive' (or clear the code manually if your dash interface allows). Start the engine to ensure no warning lights return.