John Deere 172 – ATC / C00: CLIMATRAK Outside Air Temperature Sensor Voltage Too Low

The CLIMATRAK Outside Air Temperature Sensor is reporting an output voltage below the normal operating range (less than 0.1 VDC). This low voltage indicates that the sensor's electrical resistance has dropped below 50 ohms, which corresponds to an erroneously high temperature reading of approximately 293°F (145°C). This condition points to a potential short circuit or failure within the sensor itself or its associated wiring harness.

• 6R
• 7R
• 8R
• 8RT
• 8120
• 8220
• 8320
• 8420
• 8520
• 9540
• 9560
• 9580
• 9640
• 9660
• 9680
• 9660 CTS
• 9750 STS
• 9870STS
• 4720
• 4730
• 4830
• 4940

1. 1

   Check for loose or corroded battery, starter, and ground connections

2. 2

   Check for other active diagnostic trouble codes that may be related

3. 3

   Visually inspect the outside air temperature sensor and its wiring harness for breaks, corrosion, or short circuits

4. 4

   Check the cleanliness of the A/C condenser and ensure the cab's recirculation air filter is not plugged

1. 1

   Disconnect the Battery

   To protect the tractor's computer systems, always disconnect the battery before working on electrical components.

2. 2

   Locate the Sensor

   The outside air temperature sensor is often located at the rear left corner of the cab, appearing as a small black piece hanging down. On other machines, it may be in the air intake area. Accessing it may require lifting the corner of the cab.

3. 3

   Disconnect and Test the Sensor

   Disconnect the sensor's electrical connector. You can test the sensor's resistance with a multimeter to see if it is within the manufacturer's specified range. A reading below 50 ohms would confirm the fault condition.

4. 4

   Inspect the Wiring Harness

   With the sensor disconnected, inspect the harness connector and wiring for damage or corrosion. If possible, test for continuity and for shorts to ground in the wiring harness leading back to the control unit.

5. 5

   Replace the Sensor

   If the sensor is determined to be faulty, it should be replaced. The sensor is often a grommet-style component that can be pulled out after being disconnected.

6. 6

   Reconnect and Clear Codes

   After installing the new sensor, reconnect the battery. Clear the fault codes using the tractor's diagnostic system or have a dealer do it.

7. 7

   Verify the Repair

   Operate the CLIMATRAK system and check if the fault code returns.