Kubota P2128 – Engine Control Module (ECM): Throttle/Pedal Position Sensor/Switch 'E' Circuit High

The computer detects that the voltage signal from sensor circuit 2 (or circuit 'E') is abnormally high (e.g., above 2.5V or 4.8V for a sustained period). This usually indicates a short to power, an open ground, or an internal failure of the sensor itself, causing the machine to enter a limp mode to prevent unintended acceleration.

• SVL75-2
• SVL97-2
• SVL97-3
• KX033-4
• KX057-4
• KX121-3ST
• U17-5
• U35-4
• U55
• L3240
• L3540
• L3940
• L4240
• L4740
• L5240
• L5740
• M6-101DTC
• M135XDTC
• V2403
• WG1605
• WG972

1. 1

   Connect an OBD/diagnostic scan tool to read live data and observe FPP1 and FPP2 voltages while slowly pressing and releasing the pedal to see if FPP2 reads continually high or spikes intermittently

2. 2

   Inspect the accelerator pedal connector and wiring harness for physical damage, corrosion, bent pins, or water intrusion

3. 3

   With the key ON and engine OFF, backprobe the sensor connector to verify the 5V reference voltage and ground are present, and check if the signal wire is shorted to a 5V or 12V power source

4. 4

   Perform a wiggle test on the wiring harness near the pedal while monitoring live data on the scan tool to check for intermittent shorts or loose connections

1. 1

   Turn the ignition off and disconnect the negative battery terminal to protect the ECM.

2. 2

   Locate the accelerator pedal position sensor.

   Depending on the machine, it is mounted directly on the floor pedal assembly or behind the cover for the hand-throttle/cruise control levers.

3. 3

   Press down on the release lever of the electrical plug and disconnect the harness from the sensor.

4. 4

   Remove the mounting hardware holding the sensor.

   This is typically 2 to 5 bolts/screws. Note: On some tractor models, you may need a right-angle Phillips screwdriver to access the screws. Be careful not to drop the metal spacers that the screws pass through.

5. 5

   Remove the faulty sensor from the assembly.

6. 6

   Install the new sensor.

   Use narrow needle-nose pliers if necessary to guide the spring-loaded shaft into the slot and carefully slide the spacers back into place.

7. 7

   Reinstall and tighten the mounting screws/bolts.

8. 8

   Reconnect the electrical plug to the new sensor.

9. 9

   Reconnect the battery, turn the key ON, and use your scan tool to clear the P2128 fault code.

10. 10

    Test the pedal operation to ensure smooth acceleration and verify the code does not return.