Case IH P3 – Engine Control Module (ECM) or Vehicle Control Module (VCM) / Electronic Management Unit (EMU): Foot Throttle Position Sensor, Shorted To Low Source

Signal voltage from the foot throttle position sensor has dropped below the minimum acceptable threshold. The system registers this as a 'Short to Low Source,' meaning the signal wire is likely shorted directly to ground, the sensor's internal resistance track has failed, or there is an open circuit on the reference voltage supply line.

• MXM
• Case IH MXM 120
• Case IH MXM 130
• Case IH MXM 140
• Case IH MXM 155
• Case IH MXM 175
• Case IH MXM 190
• Case IH Puma Series
• Case IH Farmall 95U
• Case IH Farmall 105U
• Case IH Farmall 115U Pro EP

1. 1

   Inspect the wiring harness leading to the foot pedal for chafing, bare wires, or pinched sections that could be shorting to the tractor cab chassis (ground).

2. 2

   Unplug the foot throttle sensor. Check for bent pins, corrosion, or moisture intrusion inside the connector.

3. 3

   Turn the key to the 'ON' position (engine off). Use a multimeter to probe the sensor connector. Verify that the sensor is receiving the correct reference voltage (typically 5V or 8V, depending on the model) and that the ground pin has good continuity to the chassis.

4. 4

   Check the signal wire from the pedal connector to the ECM/VCM harness for continuity, and verify it is not shorted to ground.

1. 1

   Disconnect Power

   Disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Remove the Sensor

   Locate the foot throttle assembly in the cab. Disconnect the electrical harness. Remove the mounting bolts securing the throttle potentiometer/sensor to the pedal assembly (on some models, the entire pedal assembly must be swapped).

3. 3

   Install the New Part

   Mount the new sensor/pedal assembly and secure the bolts. Reconnect the electrical harness.

4. 4

   Restore Power

   Reconnect the negative battery cable.

5. 5

   Clear Codes

   Use a diagnostic tool (like the Electronic Service Tool) or the tractor's H-Menu to clear the stored T3 fault code.

6. 6

   Calibrate the Sensor

   Enter the tractor's calibration mode (e.g., via the H-Menu on MXM series) and follow the on-screen prompts to cycle the pedal fully so the ECU learns the new minimum (idle) and maximum (wide-open throttle) voltage values.