Case IH t23 – Engine Electronic Control Unit (EECU) / Electronic Management Unit (EMU): Boost Air Temperature Sensor, Open Circuit Or Current Below Normal Range.

This code indicates that the controller is detecting an open circuit (such as a broken wire or disconnected plug) or a current draw that falls below the acceptable minimum threshold for the Boost Air Temperature Sensor.

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

1. 1

   Visually inspect the Boost Air Temperature Sensor electrical connector for loose pins, corrosion, or moisture.

2. 2

   Trace the wiring harness back from the sensor to the ECU, looking for chafed, broken, or melted wires that would cause an open circuit.

3. 3

   Unplug the sensor and measure its resistance with a multimeter. Typical values: 60°C = ~595 ohms, 80°C = ~322 ohms, 100°C = ~186 ohms, 120°C = ~112 ohms. If it reads completely open (infinite resistance) at room temperature, the sensor has failed internally.

4. 4

   With the key ON (engine off), probe the harness-side connector to ensure the ECU is supplying the correct 5V reference voltage and that the ground circuit is intact.

1. 1

   Power Down

   Turn off the tractor and remove the key. Disconnect the negative battery terminal if you will be repairing the wiring harness.

2. 2

   Disconnect

   Unplug the electrical connector from the Boost Air Temperature Sensor.

3. 3

   Remove Sensor

   Using an appropriately sized deep socket or wrench, carefully unthread the faulty sensor from the intake manifold or boost pipe.

4. 4

   Install New Sensor

   Thread the new Boost Air Temperature Sensor into the port. Tighten to the manufacturer's specified torque (do not overtighten, as the sensor probe is delicate).

5. 5

   Reconnect

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

6. 6

   Clear Codes

   Reconnect the battery. Turn the key to the ON position. Use the tractor's onboard "H-Menu" diagnostic display or a connected Electronic Service Tool to clear the stored t23 fault code.

7. 7

   Test

   Start the engine and allow it to reach operating temperature. Verify that the t23 code does not return and that the engine operates without derating.