Case IH U55 – Transmission Control Module (TCM) or Central Control Unit (CCM/UCM): PTO started or PTO engaged when calibrating

A calibration error code that occurs when the system detects that the Power Take-Off (PTO) was started or engaged during a calibration procedure (such as the PTO twist sensor calibration or transmission calibration). The calibration cannot proceed because the PTO must be turned off.

• Puma/Mid Range Magnum
• Maxxum
• Case IH MXM Series (MXM 120, 130, 140, 155, 175, 190)
• Case IH Puma Series
• Case IH Maxxum
• Case IH Farmall
• Case IH Steiger

1. 1

   Verify that the PTO is physically turned off during the calibration procedure.

2. 2

   Use the tractor's H-Menu (specifically the H5 switch diagnostics menu) in the transmission module to check the function of the PTO switch and see if the module is detecting its state correctly.

3. 3

   Inspect the wiring harness and the switch connection to the control module for any damage, corrosion, or loose connections.

1. 1

   Ensure the PTO is turned off and attempt to repeat the calibration procedure.

2. 2

   If the U55 code persists despite the PTO being physically off, enter the H5 diagnostic menu to test the PTO switch signal.

3. 3

   Check the wiring connection at the PTO switch and trace it back to the module to rule out a short circuit.

4. 4

   If the wiring is intact but the switch is sending an incorrect "engaged" signal (stuck closed or internally faulty), replace the PTO switch.

5. 5

   After replacing the switch, re-run the calibration procedure to confirm the fault is resolved.