Case IH t3 – Engine Control Unit (ECU) / Electronic Management Unit (EMU): Foot Throttle Position Sensor, Shorted To Low Source

The signal voltage returning from the foot accelerator pedal's potentiometer to the controller has dropped below the acceptable minimum threshold. The system interprets this abnormally low voltage as a short circuit to ground (a 'low source') or a complete open circuit on the sensor's 5V reference/signal line.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• Case IH Steiger 400 Row Trac
• Farmall 50A Compact

1. 1

   Inspect the wiring harness connecting the foot throttle position sensor to the Engine ECU for chafed wires, pinched harnesses, or melted insulation.

2. 2

   Disconnect the sensor at the pedal and inspect the connector pins for corrosion, moisture, or pushed-out pins.

3. 3

   Turn the key to the 'ON' position (engine off) and use a multimeter to verify that the sensor is receiving the correct reference voltage (typically 5V) and has a solid ground.

4. 4

   Test the signal wire between the sensor connector and the ECU for continuity to ground to determine if the wire is grounded out or if the internal potentiometer has failed.

1. 1

   Prep the Machine

   Park the tractor on a level surface, engage the parking brake, turn the key switch to the 'OFF' position, and remove the key.

2. 2

   Locate the Sensor

   Locate the foot throttle position sensor, which is mounted directly to the foot accelerator pedal assembly on the cab floor.

3. 3

   Disconnect Harness

   Carefully unplug the electrical harness connector from the throttle sensor.

4. 4

   Remove the Sensor/Pedal

   Depending on the specific model's design, remove the mounting screws/bolts securing the standalone sensor to the pedal, or remove the bolts securing the entire electronic throttle pedal mounting plate to the floor.

5. 5

   Install the New Part

   Mount the replacement sensor or pedal assembly and tighten the hardware.

6. 6

   Reconnect

   Plug the electrical harness back into the new sensor.

7. 7

   Calibration

   Turn the key switch to the 'ON' position. A potentiometer replacement often requires an Electronic Management Unit (EMU) calibration so the ECU can learn the new sensor's minimum (idle) and maximum (wide-open throttle) voltage values. Follow the specific calibration sequence in your operator's display (often accessed via the 'H-Menu' on MXM models).

8. 8

   Clear Codes

   Clear the stored fault codes and test the pedal operation to ensure code t3 does not return.