Case IH 2050 – TCM: Transmission Output Speed Sensor Short to 12V

The Transmission Output Speed (TOS) sensor monitors the rotational speed of the transmission output shaft to calculate ground/wheel speed. A 'short to high voltage' means the transmission controller is receiving a constant high voltage (such as 12V) on the sensor's signal circuit instead of the expected pulsed frequency, usually due to a wiring short or an internal sensor failure.

• Puma 165
• Puma 185
• Puma CVT
• Magnum
• Maxxum
• Farmall

1. 1

   Use the tractor's onboard diagnostic menu to confirm fault code 2050 is active and note any other related codes.

2. 2

   Locate the transmission output speed sensor on the transmission housing (e.g., top of the range transmission on Magnum models or on the transmission assembly for Puma models).

3. 3

   Visually inspect the wiring harness leading to the sensor for chafing, melting, pinched wires, or corrosion, especially near hot or moving parts.

4. 4

   Check the sensor's electrical connector for damage, corrosion, or pushed-back pins.

5. 5

   Test the Wiring Harness: Turn the ignition key to 'ON' without starting the engine. Disconnect the sensor and use a multimeter set to DC volts to probe the harness-side signal pin. If it measures approximately 12 volts, it confirms a short circuit to a power source somewhere in the harness.

6. 6

   Test the Sensor: With the sensor disconnected, use a multimeter to measure resistance (Ohms) between the sensor's terminals. A typical resistance is between 2925 and 3575 Ohms. A reading significantly out of specification or an open circuit (OL) indicates a faulty sensor.

1. 1

   Isolate the fault

   Based on the diagnostic checks, determine if the fault lies in the wiring harness or the sensor itself.

2. 2

   Repair the wiring harness

   If a short circuit is found in the harness, carefully trace the harness back to the transmission controller to find and repair the damaged section (repair insulation or replace a section of the harness). Ensure all repairs are sealed against moisture and vibration.

3. 3

   Replace the transmission output speed sensor

   If the sensor is determined to be faulty, unbolt and remove it from the transmission housing (be prepared for a small amount of oil to leak out). Install the new sensor, ensuring it is seated correctly, and securely reconnect the electrical connector.

4. 4

   Clear fault codes

   After completing the repair, use the tractor's diagnostic menu to clear the fault code.

5. 5

   Verify the repair

   Start the tractor and operate it to ensure that the fault code does not reappear and that the transmission is functioning correctly.