Case IH 179 – TMF (Tractor Management Function / Transmission Controller) or PTO Controller: The PTO is receiving no frequency from the Shaft Size Sensor on a two speed PTO.

The tractor's system is configured for a two-speed PTO, but when the PTO is switched on, the controller detects no signal (frequency) coming from the Shaft Size Sensor. Without this frequency, the controller cannot determine the installed PTO shaft size (e.g., 540 vs. 1000 RPM shaft) to properly regulate and display the speed.

• Magnum
• Case IH MX Magnum Series (MX210, MX230, MX240, MX255, MX285)
• Case IH Magnum Series (215, 225, 245, 250, 275, 280, 305, 310, 335, 340)
• Case IH Steiger Series
• Case IH Puma Series

1. 1

   Check for swapped connectors between the PTO Shaft Speed Sensor and the PTO Shaft Size Sensor (a common cause after maintenance)

2. 2

   Inspect the wiring harness at the PTO and under the controllers on the back of the cab for rodent damage or chafing

3. 3

   Verify the tractor's software is configured for a two-speed PTO (a single-speed PTO programmed as a two-speed will look for a non-existent signal)

4. 4

   Test the sensor output with an oscilloscope or advanced multimeter to check for a quasi-sinusoidal waveform when the shaft is rotating

1. 1

   Locate the Sensor

   The Shaft Size Sensor is located directly at the rear of the tractor, right at the PTO shaft housing itself (do not confuse this with the PTO Speed Sensor, which is located on top of the transmission).

2. 2

   Disconnect the Battery

   Always disconnect the battery before servicing electrical sensors to prevent short circuits.

3. 3

   Remove the Sensor

   Disconnect the electrical harness from the Shaft Size Sensor. Remove the retaining hardware (often a snap ring or a retaining bolt, depending on the exact housing).

4. 4

   Extract and Replace

   Pull the faulty sensor out of the housing. Lubricate the O-ring on the new sensor with clean hydraulic/transmission fluid and press it into place.

5. 5

   Reassemble

   Reinstall the retaining ring/bolt to secure the sensor.

6. 6

   Repair Harness (If Applicable)

   If the diagnostic phase revealed chewed wires, strip back the damaged section and use weather-sealed butt connectors to splice in replacement wire, or replace the entire Dual Speed PTO harness sub-section.

7. 7

   Clear Codes

   Reconnect the battery, turn the key on, clear the TMF fault codes from the tractor monitor, and engage the PTO to verify the fault does not return.