Case IH PD4 – PCU (Powertrain Control Unit), Armrest Controller (ARU), or Engine ECU: Hand Throttle Position Sensor Potentiometer 2 Under Voltage

The voltage signal from Potentiometer 2 of the Hand Throttle Position Sensor has dropped below the minimum acceptable threshold (under voltage). The system assumes a short to ground, an open circuit, or a failed sensor track, which typically disables the hand throttle and forces the engine into a derated 'limp home' mode.

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

1. 1

   Inspect the wiring harness and connector at the hand throttle position sensor for damaged wires, backed-out pins, or corrosion

2. 2

   Verify the sensor is receiving the correct 5V reference voltage and a solid ground from the controller with the key in the ON position

3. 3

   Test the signal wire for Potentiometer 2 between the sensor connector and the PCU/Armrest controller for an open circuit or a short to ground

4. 4

   Perform a potentiometer sweep test using a multimeter to measure the resistance/voltage sweep while slowly moving the hand throttle from idle to maximum (voltage should transition smoothly without dropping out)

1. 1

   Safety First

   Turn off the tractor, remove the key, and allow the machine to cool down.

2. 2

   Access the Sensor

   Remove the trim panels on the armrest console to access the underside of the hand throttle lever assembly.

3. 3

   Remove the Faulty Sensor

   Disconnect the electrical harness connector from the hand throttle potentiometer. Unbolt the potentiometer from the throttle lever mechanism.

4. 4

   Install the New Part

   Mount the replacement hand throttle potentiometer to the lever assembly and reconnect the electrical harness.

5. 5

   Reassemble

   Reinstall the armrest console trim panels.

6. 6

   Perform Calibration

   Enter the tractor's H-Menu (Calibration Mode) and perform the Hand Throttle Potentiometer Calibration. This teaches the controller the new minimum (idle) and maximum voltage values for the new sensor.

7. 7

   Clear Codes

   Clear the stored fault codes from the PCU/ECU and test the hand throttle operation to ensure the engine RPM responds correctly without throwing a new code.