Case IH 3122 - UCM – ECM / EDC or UCM: PTO Twist Sensor - Short circuit to Ground

The signal voltage from the Power Take-Off (PTO) twist sensor is being improperly routed to ground, likely due to a compromised wiring harness, a damaged connector, or an internal short within the sensor itself.

• MAXXUM T4E
• Case IH Magnum Series (225, 235-340 Series 4)
• Case IH Puma Series (165, 180, 195, 210, 225 CVX)
• Case IH Maxxum Series (120 Tier 3 Pro)
• Case IH Farmall Series (115U)

1. 1

   Inspect the wiring harness and connectors leading to the PTO twist sensor for chafing, bare wires, or moisture that could cause a short to ground.

2. 2

   Disconnect the PTO twist sensor and test the harness side to isolate the short. If the short remains, the wiring harness is the issue. If the short disappears, the sensor has failed internally.

1. 1

   Resolve the Short

   Repair any damaged sections of the wiring harness or replace the faulty connector.

2. 2

   Replace the Sensor

   If the harness tests good, remove the faulty PTO twist sensor and install the replacement sensor. Ensure you use a new copper sealing washer during installation.

3. 3

   Perform Calibration

   Once the sensor is replaced (or if the UCM is replaced), the system will require calibration. If not calibrated, the tractor will throw a subsequent fault code 3123 (PTO Twist Sensor - Not Calibrated).

4. 4

   Calibration Sequence

   Depending on the model, run the auto-calibration mode where the flywheel twist sensor, PTO twist sensor, and transmission clutches are calibrated in sequence. If an error occurs during this auto mode, the sequence stops and displays a code, which can be cleared using the upshift/downshift buttons.