Case IH 2051 (177.03) – Transmission Control Unit (TCU) / Transmission Control Module (TCM): Oil temperature sensor open circuit / Transmission Oil Temperature Sensor Circuit Failed Open or High

The transmission oil temperature sensor is a negative temperature coefficient (NTC) thermistor. If the sensor's internal circuit breaks (fails open), or if the wiring harness is severed or shorted to a high voltage source (like the 5V supply or battery voltage), the controller registers an abnormally high voltage signal above the critical maximum value.

• VESTRUM CVX
• MX100
• MX110
• MX120
• MX135
• MX150
• MX170
• Maxxum 135
• Magnum 235 - 380
• Vestrum 100 CVX
• Farmall 30C
• Farmall 40C
• Farmall 95U
• Farmall 105U
• Farmall 115U
• Farmall 130A
• Steiger
• Puma

1. 1

   Visually inspect the transmission oil temperature sensor connector and the transmission strip harness for water ingress, poor terminal contact, or physical wire damage.

2. 2

   Disconnect the sensor from the machine harness and measure the resistance across the pins on the sensor side. An open circuit (infinite resistance) indicates the sensor has failed internally.

3. 3

   With the key start switch in the ON position and the sensor disconnected, measure the voltage at the machine harness connector between the supply pin and the ground pin (or chassis ground). The expected result is approximately 5 VDC.

4. 4

   If the voltage is not 5 VDC, check the machine harness for an open in the supply circuit or verify if the ECU has failed.

1. 1

   Turn the ignition switch off and disconnect the battery to prevent electrical shorts.

2. 2

   Locate the transmission oil temperature sensor on the transmission housing or valve block.

3. 3

   Disconnect the electrical connector from the sensor.

4. 4

   Place a drain pan underneath the sensor area, as removing the sensor may allow transmission fluid to escape.

5. 5

   Unscrew and remove the faulty transmission oil temperature sensor.

6. 6

   Install the new sensor into the transmission housing.

7. 7

   Reconnect the electrical harness connector securely to the new sensor.

8. 8

   Check the transmission fluid level and refill the transmission oil if any was lost during the sensor swap.

9. 9

   Reconnect the battery, turn the ignition ON, and clear the fault codes.

   Verify that the SPN 177 FMI 3 / 2051 code does not return.