Case IH tC4 – PCU (Powertrain Control Unit): Engine Torque/RPM Sensor Open Circuit

The Engine Torque/RPM sensor measures engine speed and torque by monitoring the deflection of the flywheel damper springs. The system uses this torque data to determine the optimal timing for gear shifts. An open circuit indicates that the controller has lost the electrical signal from this sensor.

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

1. 1

   Verify Connector Placement: Ensure the Engine Torque/RPM sensor connector (C255) has not been accidentally swapped with the transmission mid-speed sensor (C037) or the output speed sensor (C038).

2. 2

   Harness Continuity Test: Power OFF the machine and disconnect the battery/pull the fuse. Disconnect the torque sensor connector (C255) and the PCU connectors (C100 and C101). Using a multimeter, trace and check the wiring (e.g., from pin C101-11 to C255-2) for an open circuit or a short to ground.

3. 3

   Mechanical Inspection: If the wiring is intact, inspect the flywheel damper fingers mechanically. Damaged damper fingers can cause erratic readings or signal loss.

1. 1

   Repair Wiring

   If the multimeter test reveals a break in the harness between the PCU and the sensor, repair or replace the affected wiring harness section.

2. 2

   Replace Sensor

   If the wiring and connectors are verified good, the internal coil of the Engine Torque/RPM sensor has likely failed open. Remove the faulty sensor from the flywheel/transmission input housing and install a new sensor.

3. 3

   Address Mechanical Damage

   If the flywheel damper fingers are bent or damaged during inspection, the tractor will need to be split to replace the flywheel damper assembly.

4. 4

   Clear Codes & Calibrate

   Clear the tC4 error code from the PCU memory. Perform a flywheel damper torque calibration. (On MXM/TM models, this typically involves entering the H-Menu calibration mode, pressing and holding the downshift button while the display shows 'dt', and allowing the engine speed to automatically set to 1200 RPM until the display shows 'End'). Test the system for normal operation.