Case IH tC2 – Transmission / EDC (Electronic Draft Control) Controller: PTO Twist Sensor Open Circuit

The control module has detected a break in the electrical circuit (infinite resistance or lack of continuity) for the PTO twist sensor, which monitors the torque and speed of the PTO shaft.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190

1. 1

   Inspect the wiring harness leading to the PTO twist sensor (located at the rear of the transmission/PTO housing) for visible breaks, chafing, or rodent damage.

2. 2

   Disconnect the sensor and inspect the 3-pin connector for damaged, bent, corroded, or dislocated pins.

3. 3

   Use a multimeter to check the continuity of the wiring from the sensor connector back to the Transmission/EDC controller. Check for a short to chassis ground.

4. 4

   Measure the internal resistance of the PTO twist sensor. A completely open reading (infinite ohms) confirms the sensor itself has failed internally.

1. 1

   Preparation

   Ensure the tractor is turned off, the parking brake is applied, and the key is removed.

2. 2

   Wiring Repair (If Applicable)

   If the diagnostic checks reveal a broken wire or a damaged connector, splice in a new 3-pin connector pigtail and seal it with heat-shrink tubing.

3. 3

   Sensor Replacement

   If the wiring tests good but the sensor is open, remove the retaining bolt(s) holding the PTO twist sensor in the transmission housing and pull the sensor out.

4. 4

   Installation

   Install the new PTO twist sensor. (Note: Some Case IH service bulletins note that if a speed/twist sensor does not engage deeply enough, removing the O-ring and using Teflon tape on the threads can resolve seating issues, though you should attempt standard OEM installation first).

5. 5

   Reconnection

   Plug the electrical harness back into the sensor.

6. 6

   Recalibration

   Clear the fault codes. After replacing the sensor, you will likely trigger a U50 fault code ("PTO twist sensor not calibrated"). You must perform the Transmission/PTO calibration procedure (often accessed via the H-Menu / H1 calibration mode) to sync the new sensor with the controller.