Case IH 2385 – Transmission Control Module (TCU): Inconsistent relationship between transmission output speed and engine speed

When the machine exits Auto mode, the system detects that the transmission output speed does not match the expected value based on the engine's RPM. This underlying condition is typically caused by either a failing transmission speed sensor or internal mechanical transmission slippage.

• Puma/Mid Range Magnum
• Optum
• Puma Series (Puma 145, Puma 165)
• Magnum Series (180, 200, 220, 225, 240, 250, 280, 310, 340, 380)
• Maxxum Series (115, 125, 130, 140)
• Farmall Series (60A)
• Steiger Series

1. 1

   Isolate the Gear: Determine if the fault code sets in a specific gear or across all gears. If it only happens in one specific gear, the issue is likely mechanical slippage (e.g., a worn clutch pack) rather than a faulty sensor.

2. 2

   Sensor Wiring Inspection: Check the wiring harness and connector leading to the transmission output speed sensor for corrosion, moisture, bent pins, or a loss of ground connection.

3. 3

   Sensor Testing: Test the transmission speed sensor's signal output to verify if it is dropping out or providing erratic readings when transitioning out of Auto mode.

4. 4

   Transmission Calibration: Attempt a transmission calibration procedure to see if the synchronizers can be successfully re-calibrated.

1. 1

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

2. 2

   Locate the transmission output speed sensor on the transmission housing/rear axle housing.

3. 3

   Disconnect the electrical harness plug from the sensor.

4. 4

   Remove the retaining bolt holding the sensor in place and carefully pull the old sensor out of the transmission housing.

5. 5

   Lubricate the O-ring on the new OEM transmission speed sensor with clean transmission fluid.

6. 6

   Insert the new sensor into the housing and tighten the retaining bolt to OEM torque specifications.

7. 7

   Reconnect the electrical harness, ensuring the plug clicks securely into place.

8. 8

   Clear the fault codes from the TCU using a diagnostic tool.

9. 9

   Test drive the tractor, specifically engaging and exiting Auto mode, to ensure the speed readings remain consistent and the code does not return.