Kubota P0112 – Engine Control Module (ECM) / Engine ECU: Intake Air Temperature (IAT) Sensor 1 Circuit Low

The engine computer is receiving an abnormally low voltage signal (typically 0.05 V or less for 2.8 seconds or more) from the IAT sensor, indicating a direct short to ground in the sensor or the wiring harness.

• KX040-4
• KX057-4
• KX080-4
• U48-5
• U55-4
• U55-5
• SSV65
• SSV75
• SVL65-2
• SVL75-2
• SVL90-2
• SVL95-2S
• SVL97-2
• L3301
• L3901
• L4060
• L4701
• M5 series
• M6 series
• D1803
• V1505
• V1803
• V2403
• V2607
• V3307
• V3800

1. 1

   Connect an OBD2/J1939 scan tool and read live data for the Intake Air Temperature to check for impossibly high temperatures or voltage near 0V

2. 2

   Visually inspect the IAT/MAF sensor and its 5-pin connector for pushed-out pins, water intrusion, or wire chafing

3. 3

   Perform a reference voltage test by disconnecting the sensor, turning ignition ON (engine OFF), and verifying the ECM supplies a ~5V reference voltage

4. 4

   Perform a short to ground test by measuring resistance between the sensor's signal wire and chassis ground (continuity indicates a shorted harness)

5. 5

   Perform a sensor resistance test across the sensor's terminals and compare to factory specs for the current ambient temperature (near 0 ohms indicates an internal short)

1. 1

   Turn off the machine's ignition and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   If the diagnostic tests revealed a short in the wiring harness, trace the harness back to the ECM, locate the chafed/damaged section, and repair the wires.

3. 3

   If the wiring is intact and the sensor failed the resistance test, locate the IAT/MAF sensor on the engine's air intake pipe or air cleaner assembly.

4. 4

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

5. 5

   Remove the mounting screws securing the sensor to the intake housing and carefully pull the sensor out.

6. 6

   Insert the new OEM sensor, ensuring the O-ring or seal is seated properly to prevent vacuum leaks.

7. 7

   Tighten the mounting screws and reconnect the electrical harness.

8. 8

   Reconnect the battery, turn the ignition on, and use a scan tool to clear the P0112 / SPN 172 FMI 4 fault code.

9. 9

   Start the engine and verify that the check engine light remains off and live data shows an accurate ambient intake temperature.