Case IH U27 – Transmission Control Module: C3 calibration value is too low

During the transmission's automated calibration process, the controller increases hydraulic pressure to the C3 clutch and monitors the engine RPM to determine the clutch fill time and engagement point. The U27 code is triggered when the engine RPM drops too soon, meaning the initial test pressure pulled down the engine prematurely before the expected calibration value was reached.

• Maxxum
• Maxxum 100
• Maxxum 110
• Maxxum 115
• Maxxum 120
• Maxxum 125
• Maxxum 130
• Maxxum 140
• Maxxum 155
• Maxxum 175
• Maxxum 190
• MX170
• MX210
• MX230
• MX255
• MX285
• Puma Series
• Farmall Series

1. 1

   Verify Calibration Conditions: Ensure the tractor is parked on a flat surface, the parking brake is set, and all implements are disconnected.

2. 2

   Check Engine Stability: Ensure the engine speed is stable and absolutely no throttle adjustments are made while the calibration is running.

3. 3

   Fluid Temperature: Ensure the transmission fluid is at normal operating temperature, as cold fluid can cause premature RPM drop during calibration.

4. 4

   Solenoid Testing: Check the C3 clutch solenoid valve (EDC valve) for proper operation. Swap the C3 solenoid with the C4 solenoid to see if the fault follows the valve.

5. 5

   Manual Quickfill Test: If supported by the model's H-menu, perform a manual quickfill test to see if engagement noise can be heard when engaging C3, which helps verify if hydraulic pressure is actually reaching the clutch pack.

1. 1

   Re-attempt Auto Calibration

   Enter the tractor's H-Menu (e.g., H8 procedure or 16x16 Transmission Auto Calibration) and run the calibration again without touching the throttle.

2. 2

   Manual Calibration

   If auto-calibration fails, enter the manual calibration mode (if available on your specific model) to manually adjust the fill times for the C3 clutch.

3. 3

   Inspect/Replace the Solenoid

   If the clutch pressure is not being controlled properly, remove and inspect the C3 PWM solenoid valve. If it is sticking or electrically faulty, replace it.

4. 4

   EDC Valve Calibration

   If a new EDC solenoid valve or control module is fitted, you must perform the EDC Valve Calibration Procedure.

5. 5

   Mechanical Inspection

   If the solenoid is functioning correctly but the code persists, apply shop air pressure to the C3 clutch pressure port to listen for internal leaks or piston movement. If air escapes or the piston does not move, the transmission will require a teardown to inspect the C3 clutch pack (friction plates, pressure plate, and seals) for mechanical failure breaking the torque path.