Case IH tC7 – PCU (Power Control Unit): No Signal From The PTO Twist Speed Sensor

The control module is not receiving a valid speed or torsion signal from the sensor monitoring the PTO driveline, which is necessary to calculate PTO speed and torque.

• MXM
• Case IH MXM Series (MXM 120, 130, 140, 155, 175, 190)
• Case IH Puma Series
• Case IH Magnum Series

1. 1

   Visually inspect the PTO twist speed sensor and the engine torque/RPM sensor to ensure they are not installed incorrectly, loose, or physically damaged.

2. 2

   Inspect the wiring harness leading to the sensor for open circuits, shorts to ground, or chafing.

3. 3

   Check for a mechanical fault in the driveline by inspecting the flywheel damper fingers and the PTO twist sensor phonic wheel for damage.

4. 4

   Use the tractor's diagnostic test switch (Tool 380000488) in diagnostic connector C125 to access the 'H-Menu' and view live sensor values to confirm if the signal is completely dead or just out of calibration.

1. 1

   Repair Wiring

   If the wiring harness is damaged, cut away the damaged section. Twist the bare leads together, solder them, and apply a silicon rubber compound (non-hardening sealant) over the repaired section. Cover the area with insulating tape, overlapping at least 2 inches (50 mm) on each side.

2. 2

   Replace the Sensor

   If the wiring is intact but the sensor is dead, remove the faulty PTO twist speed sensor from its mounting port and install a new one.

3. 3

   Repair Mechanical Damage

   If the diagnostic inspection revealed damage to the phonic wheel or flywheel damper fingers, these mechanical components must be repaired or replaced for the new sensor to read correctly.

4. 4

   Calibrate the New Sensor

   Enter the tractor's calibration mode. Navigate until the display shows 'Pt' (PTO twist calibration). Press and hold the downshift button to calibrate the PTO twist sensor. The calibration is successful when the display alternates between 'Pt' and the new calibration value.