Case IH 2578 – UCM (Universal Control Module): Wheel speed (transmission output speed) sensor #2 - no signal

The control module expects a speed reading from the #2 transmission output speed sensor but receives no signal. The system specifically logs this code when there is a lack of signal, but it does not detect a direct short to 12V or a short to ground.

• Optum
• Case IH Puma Series
• Case IH Steiger Series
• Case IH Magnum Series

1. 1

   Inspect the wiring harness and connector between the UCM and the #2 transmission output speed sensor for open circuits, loose pins, or damaged wires.

2. 2

   Remove the sensor and check the magnetic tip for accumulated metal shavings from the transmission that could block the signal.

3. 3

   Verify the sensor's mounting depth and air gap, as improper seating or a backed-out sensor can cause signal loss.

4. 4

   Clear the error code using the diagnostic interface and test the system by driving at or above third gear for at least 30 seconds to see if the code returns.

1. 1

   Preparation

   Park the machine on a level surface, engage the parking brake, turn off the engine, and turn the battery disconnect switch to the OFF position.

2. 2

   Locate the Sensor

   Locate the Transmission Output Speed Sensor #2 on the transmission housing.

3. 3

   Removal

   Disconnect the 4-way electrical connector from the sensor. Remove the retaining bolt and carefully pull the sensor out of the transmission housing.

4. 4

   Clean and Prep

   Clean the mounting port on the transmission to ensure the new sensor will seat perfectly flat (preventing air gap issues).

5. 5

   Installation

   Lubricate the O-ring/seal on the new sensor. Insert the new sensor into the housing and tighten the retaining bolt to OEM torque specs.

6. 6

   Reconnection

   Reconnect the electrical harness. Ensure the locking tab on the connector clicks into place.

7. 7

   Calibration/Clearing

   Turn the battery disconnect and key switch back to the ON position. Access the UCM/Transmission controller via the diagnostic menu and clear the inactive 2578 fault code.

8. 8

   Validation

   Operate the tractor to verify the UCM is successfully reading the transmission output speed and that the code does not return.