John Deere 1172.12 – ECU (Engine Control Unit): The Intake Air Temperature Sensor Has A Fault / Intake Air Temperature Error

This code indicates a problem with measuring the intake air temperature. The Engine Control Unit (ECU) is receiving faulty readings, which can result from a malfunctioning sensor, damaged wiring, or an internal ECU problem. When this code is active, the ECU may limit engine performance or adjust air-fuel mixture parameters to compensate for the faulty readings, which can negatively affect engine efficiency and emissions.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• 5090M
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 8225R
• 8245R
• 8270R
• 8295R
• 8310R
• 8310RT
• 8320R
• 8335R
• 8335RT
• 8345R
• 8360RT
• 8370R
• 7210R
• 7230R
• 7250R
• 7270R
• 7290R
• 7310R
• 7180
• 7280
• 7380
• 7480
• 7580
• 7780
• 7980
• S670
• S690
• T550

1. 1

   Inspect the intake air temperature sensor for physical damage, heavy soot buildup, or malfunction, and ensure it is securely connected.

2. 2

   Examine the wiring harness and connectors related to the intake air temperature sensor for signs of chafing, damage, corrosion, or loose pins.

3. 3

   Use a diagnostic tool or multimeter to test the signal voltage and resistance from the temperature sensor, comparing live readings to expected values.

4. 4

   Check the ECU for internal faults if the sensor tests within specification and the wiring harness has good continuity with no shorts.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery to prevent electrical shorts during repair.

2. 2

   Repair Wiring (If Applicable)

   If the diagnostic checks revealed damaged wiring or corroded connectors, repair or replace the affected harness sections.

3. 3

   Replace Faulty Sensor

   If the sensor failed the signal test, unplug the electrical connector, unthread the defective intake air temperature sensor from the intake manifold/piping, and install a new sensor. Torque to OEM specifications.

4. 4

   Reconnect and Reset

   Reconnect the sensor harness and the battery.

5. 5

   Clear Codes and Verify

   Use a diagnostic tool to reset the ECU and clear the 001172.12 error code. Run the engine and monitor the live intake air temperature data to ensure the sensor operates correctly and the code does not return.