Case IH 2051(177.03) - DEC – DEC: Transmission Oil Temperature Sensor Circuit Short to High Voltage or Open Circuit

The controller monitors the voltage drop across the sensor to determine the oil temperature. If the voltage at the signal input is too high (typically reading the full 5-volt reference with no drop), the system flags an open circuit or a short to a positive lead, meaning the controller cannot read the actual transmission oil temperature.

• MAXXUM T4E
• Maxxum series
• Farmall series (95U, 105U, 105C, 115U)
• MX series (MX100, MX110, MX120, MX135)
• Magnum and Steiger series

1. 1

   Locate the transmission oil temperature sensor on the transmission housing and visually inspect the sensor and its connector for physical damage, corrosion, or moisture.

2. 2

   Inspect the wiring harness leading from the sensor back to the DEC/TCU. Look for chafed wires shorting to a power source, specifically checking the signal wire (e.g., wire 7500) and the earth/ground wire (e.g., wire 60AD).

3. 3

   Disconnect the sensor, turn the key ON, and measure the voltage at the connector to verify a 5V reference signal is present.

4. 4

   Test the ground pin for continuity to the chassis/controller ground. If the wiring is intact and the 5V reference is present but the code persists, the sensor itself has failed internally (open circuit).

1. 1

   Park the tractor on a level surface, engage the parking brake, and turn off the engine.

2. 2

   Clean the area around the transmission oil temperature sensor to prevent dirt from entering the transmission housing.

3. 3

   Disconnect the electrical wiring harness from the sensor.

4. 4

   Place a drain pan underneath the sensor area, as a small amount of transmission fluid may leak out when the sensor is removed.

5. 5

   Using an appropriately sized wrench or deep socket, unthread and remove the faulty transmission oil temperature sensor.

6. 6

   Install the new OEM transmission oil temperature sensor.

   Thread it in by hand to prevent cross-threading, then tighten it to the manufacturer's specified torque.

7. 7

   Reconnect the electrical harness, ensuring the locking tab clicks into place.

8. 8

   Check the transmission fluid level and top off if any significant amount was lost during the swap.

9. 9

   Clear the fault codes using a diagnostic tool or the tractor's onboard diagnostic menu.

10. 10

    Start the tractor and operate it until the transmission oil reaches operating temperature (greater than 60°C / 140°F) to verify that the sensor is reading correctly and the code does not return.