Case IH P4 – Engine ECU: Foot Throttle Position Sensor, Shorted To High Source

The signal voltage returning from the Foot Throttle Position Sensor is higher than the maximum expected normal operating range. The system is detecting a 'Shorted to High Source' condition, which typically means the sensor's signal circuit is shorted directly to a power source (+8V or +12V), the sensor has lost its ground connection, or the potentiometer has failed internally.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• Farmall 50A
• Farmall 70A
• Farmall 95U
• Farmall 105U
• Farmall 115U Pro EP
• Puma
• Maxxum
• Magnum

1. 1

   Stop the engine and let it cool before starting work. Do not start the engine during these service procedures.

2. 2

   Visually inspect the foot throttle position sensor harness and connector (e.g., Connector X-321 on Farmall models) for physical damage.

3. 3

   Inspect for moisture or debris inside the connector terminals, which is a highly common cause of shorts to high voltage (often from pressure washing).

4. 4

   Check for any damaged or loose machine earths (grounds) and ensure no connector pins are pushed back or corroded.

5. 5

   Use a multimeter to verify if the signal wire is shorted to an +8V or +12V source.

1. 1

   Disconnect Power

   Turn the key switch to the OFF position and disconnect the battery to protect the ECU.

2. 2

   Clean/Repair Wiring

   If water or debris was found in the sensor connector, clean the terminals thoroughly with electrical contact cleaner and apply dielectric grease. Repair any chafed wires in the harness that may be bridging the signal wire to a power wire.

3. 3

   Replace Sensor

   If the wiring harness and grounds test perfectly, the potentiometer itself has failed internally and must be replaced. Unbolt the faulty sensor from the foot pedal assembly and install the new unit.

4. 4

   System Calibration

   After a potentiometer has been replaced, or if the non-volatile memory has been reset, a Transmission/EDC calibration is required.

5. 5

   Reset Procedure

   Initialize the new sensor by disconnecting the potentiometer with the key switch in the 'ON' position, and then re-connecting it. Follow up with your specific model's H-Menu calibration to ensure clutch featherability and shift quality are restored.