Case IH 2578 (3825.02) - DEC – Transmission Controller (TCU): Transmission Output Speed Sensor #2 Failure

The transmission electronic control module (ECM/TCU) has detected that the signal from the Transmission Output Speed Sensor #2 is erratic, intermittent, incorrect, or completely missing.

• MAXXUM T4E
• VESTRUM CVX
• Steiger
• Magnum
• Puma
• Maxxum
• MX Series
• MX100
• MX110
• MX120
• MX135
• MX255
• T7
• T8
• T9

1. 1

   Connect the Electronic Service Tool (EST) laptop and monitor 'TRANS TRANSMISSION OUTPUT SHAFT SPEED' parameters while operating the tractor to see if the sensor reading drops out or fluctuates erratically

2. 2

   Inspect the 3-wire pin connector at the sensor for corrosion, moisture, or pushed-back pins

3. 3

   Check the wiring harness between the sensor and the Transmission Controller for continuity, open circuits, or shorts to ground/12V

4. 4

   Verify the sensor's physical installation to ensure there is no 'critical air gap' caused by the sensor backing out or being too far from the transmission tone ring

5. 5

   Rule out mechanical transmission slippage (e.g., slipping clutch pack) which can cause output speed to mismatch commanded input speed and trigger plausibility faults

1. 1

   Park the machine on a level surface, engage the parking brake, and turn off the engine.

2. 2

   Disconnect the negative battery terminal to prevent short circuits while working on the electrical system.

3. 3

   Locate the Transmission Output Speed Sensor #2.

   It is typically mounted on the transmission housing near the output shaft or the rear differential/axle housing.

4. 4

   Unplug the 3-wire electrical connector from the sensor.

5. 5

   Remove the retaining bolt or nut securing the sensor to the housing.

6. 6

   Carefully pull the old sensor out of the bore.

   Note: Have a shop rag ready, as a small amount of transmission/hydraulic fluid may weep out.

7. 7

   Inspect the mounting bore and wipe away any dirt or metallic debris.

   Ensure the new sensor has a lubricated O-ring installed.

8. 8

   Insert the new speed sensor into the bore and secure it with the mounting bolt.

   Do not over-torque, as this can crack the plastic sensor housing.

9. 9

   Reconnect the 3-wire electrical connector, ensuring it clicks firmly into place.

10. 10

    Reconnect the battery, turn the key on, and use the EST or in-cab display to clear the inactive fault codes.

    Test drive the tractor to verify the speedometer and transmission shifting operate correctly.