Case IH 5027 - UCM – UCM: Rear PTO speed sensor – open circuit

This fault code indicates a complete loss of electrical continuity (an open circuit) in the rear Power Take-Off (PTO) speed sensor circuit. The control module is unable to detect the sensor, which usually points to a disconnected plug, a severed wire in the harness, or a sensor that has failed internally and broken the circuit.

• MAXXUM T4E
• Puma Series (115, 165, 180, 195, 210, 225 CVX, 240)
• Maxxum Series (100, 110, 115, 120, 125, 130, 140)
• Magnum Series (180, 190, 210, 225, 250, 305, 315)
• Farmall Series (85C, 95C, 95U, 105U, 115U)
• Optum Series (250, 270, 300)

1. 1

   Visually inspect the Rear PTO speed sensor and wiring harness for physical damage, rubbing, or severed wires.

2. 2

   Disconnect the sensor plug and inspect the pins for corrosion, moisture, or pushed-out terminals.

3. 3

   Perform a wiring continuity test using a multimeter to check the harness back to the UCM (Pin 1: PTO Supply, Pin 2: Signal, Pin 3: Ground).

4. 4

   If the harness has perfect continuity and supplies the correct reference voltage/ground, test the sensor itself for an internal open circuit.

1. 1

   Preparation

   Park the tractor on a level surface, turn off the engine, and remove the key.

2. 2

   Clean the Area

   Thoroughly clean the area around the rear PTO housing where the speed sensor is mounted to prevent dirt from entering the transmission housing.

3. 3

   Remove the Sensor

   Disconnect the electrical connector. Remove the retaining bolt holding the sensor in place. Carefully pull the sensor straight out of the housing. (Have a rag ready, as a small amount of hydraulic/transmission fluid may weep from the port).

4. 4

   Install the New Sensor

   Lubricate the O-ring on the new sensor with clean transmission fluid. Push the sensor into the bore until fully seated and install the retaining bolt.

5. 5

   Reconnect

   Plug the electrical connector back in, ensuring it clicks and locks securely.

6. 6

   Clear and Test

   Turn the key on, clear the fault codes from the UCM/Armrest display, and start the tractor. Engage the rear PTO to verify that the speed registers correctly on the dash/monitor and that code 5027 does not return.