Case IH U31 – Transmission Control Unit (TCU): Output Speed Sensed - Tractor Moving

This fault code is triggered during transmission or clutch calibration procedures. It indicates that the transmission control system is detecting rotational movement from the transmission output speed sensor when the tractor is supposed to be completely stationary for the calibration to proceed.

• Puma/Mid Range Magnum
• Farmall
• Maxxum
• MXM
• MXM Series
• Puma Series
• Maxxum Series
• Magnum Series

1. 1

   Verify Immobilization: Ensure the handbrake is fully applied and the wheels are physically chocked.

2. 2

   Brake Function Test: Ensure the tractor's brakes are actually holding the machine. If the brakes are working properly, move the vehicle forward slightly, stop, and attempt the calibration again.

3. 3

   Connector Verification: Check the wiring harness at the transmission. Ensure the connectors for the transmission mid speed sensor and the transmission output speed sensor have not been accidentally swapped.

1. 1

   Immobilize tractor

   Apply the handbrake and chock the wheels to ensure the tractor cannot move.

2. 2

   Test brakes and retry calibration

   If the brakes are functioning normally, move the tractor forward slightly, stop, and repeat the calibration procedure.

3. 3

   Locate speed sensors

   If the U31 error code is still displayed, locate the transmission mid and output speed sensors on the transmission housing.

4. 4

   Inspect wiring harness and connectors

   Inspect the wiring harness and connectors. Ensure the mid and output speed sensor connectors are plugged into their correct respective sensors and have not been swapped.

5. 5

   Inspect sensor wiring

   Inspect the sensor wiring for chafing, shorts, or damage.

6. 6

   Inspect and replace output speed sensor

   If the connectors are routed correctly and the wiring is intact, remove and inspect the transmission output speed sensor. Replace the sensor if it is faulty or damaged.

7. 7

   Check for internal mechanical fault

   If the sensors and wiring are functioning correctly, the service manual notes there is a possible internal mechanical fault within the transmission causing the output shaft to rotate.

8. 8

   Clear error code and test

   Once the root cause is rectified, clear the error code and test the system for normal operation.