Case IH 75 – Transmission Control Unit (TCU) or Central Control Unit (CCU): Shaft 3 speed sensor fault

The control module is receiving an erratic signal, an out-of-range signal, or no signal at all from the speed sensor monitoring Shaft 3. The controller detects that the shaft speed does not match the expected parameters.

• STX Steiger
• Farmall 55A/C
• Farmall 65A/C
• Farmall 75A/C
• Farmall 75N
• Farmall 85C
• Farmall 95C
• Farmall 115U
• Axial-Flow 2388
• Steiger
• Quadtrac
• Magnum
• Maxxum

1. 1

   Check battery voltage with the engine running at 2000 RPM to ensure it is stable and not spiking above 15 Volts.

2. 2

   Inspect the wiring harness and connectors between the Shaft 3 speed sensor and the ECU/CCU for damage, ensuring pins are tight and fully seated.

3. 3

   Perform a continuity test on the wiring harness with a multimeter to rule out an open circuit or short to ground.

4. 4

   Verify the sensor is mounted securely and has the correct air gap.

5. 5

   Remove the sensor and inspect the magnetic tip for a heavy buildup of metallic debris or shavings that could blind the sensor.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical shorts.

2. 2

   Locate the Sensor

   Locate the Shaft 3 speed sensor on the transmission housing or PTO housing (refer to the specific model's service manual for exact placement).

3. 3

   Disconnect

   Unplug the electrical connector from the sensor harness.

4. 4

   Remove

   Remove the retaining bolt holding the sensor in place. Carefully twist and pull the sensor out of the housing. Have a shop towel ready, as a small amount of transmission/hydraulic fluid may seep out.

5. 5

   Install New Sensor

   Lubricate the O-ring on the new speed sensor with clean transmission fluid. Insert the sensor into the bore until fully seated.

6. 6

   Secure

   Install the retaining bolt and torque to the specification listed in your model's service manual.

7. 7

   Reconnect

   Plug the electrical connector back into the sensor, ensuring it clicks and locks into place.

8. 8

   Clear Codes

   Reconnect the battery. Use the Case IH Electronic Service Tool (EST) to clear the inactive fault code 75 from the module's memory.

9. 9

   Test Operation

   Start the tractor and return the machine to operation to verify the fault code does not return and the shaft speed registers correctly on the display.