Case IH 3122 (517801.04) - DEC – Engine Control Module (ECM): PTO Twist Sensor - Short circuit to Ground

The controller monitoring the rear Power Take-Off (PTO) system has detected that the signal voltage from the PTO twist sensor has dropped below the minimum acceptable threshold, meaning the signal wire is shorted directly to a ground source.

• VESTRUM CVX
• Case IH Magnum Series: 210, 220, 235–340 (Series 4), 240, 255, 285
• Case IH Puma Series: 165, 180, 195, 210, 225, 180-260 CVX

1. 1

   Visually inspect the PTO twist sensor wiring harness (connector X-300) at the rear PTO driveline for chafing, pinched wires, or melted insulation.

2. 2

   Disconnect the 3-pin connector at the sensor and check for water ingress, dirt, or bent/corroded pins that could bridge the signal and ground terminals.

3. 3

   Isolate the harness from the sensor: with the sensor disconnected, turn the key ON and use a multimeter to check if the short to ground is still present on the harness side.

1. 1

   Power Down

   Turn off the tractor, remove the key, and ensure all electrical and hydraulic applications are deselected.

2. 2

   Disconnect

   Unplug the 3-pin electrical connector (X-300) from the PTO twist sensor.

3. 3

   Repair/Replace

   If wiring is damaged: Splice and repair the damaged section of the chassis harness or replace the 3-pin connector. If the sensor is faulty: Unbolt the faulty PTO twist sensor from its mounting location on the rear PTO housing and remove it. Install the new sensor and tighten the mounting hardware.

4. 4

   Reconnect

   Plug the 3-pin connector back into the sensor.

5. 5

   Calibrate

   You must perform a PTO twist sensor calibration after replacement. Installing a new sensor without calibrating it will immediately trigger a secondary fault code: 3123 (U70) - PTO Twist Sensor - Not Calibrated. Follow the tractor's specific display monitor or service tool procedure to calibrate the sensor. Ensure the PTO is turned OFF during the calibration process, or it will fail (Error U55).