Kubota P2126 – Engine Control Module (ECM) / Engine Control Unit (ECU): FPP1 Higher Than FPP2

The Engine Control Module (ECM) detects that the percentage deflection or voltage of sensor 1 (FPP1) is greater than sensor 2 (FPP2) by more than 20.0% for longer than 1.5 seconds. This triggers the Malfunction Indicator Lamp (MIL) and forces the engine into a Power Derate or Low Rev Limit mode to prevent unintended acceleration.

• WG1605
• WG2503
• WG3800
• WG972
• D1105
• D1803

1. 1

   Connect a diagnostic scan tool to the Kubota Service Port (KSP) and monitor live data for FPP1 and FPP2 while slowly depressing the pedal to check for a divergence of >20%.

2. 2

   Inspect the physical foot pedal mechanism in the operator's compartment for debris, mechanical binding, or damage.

3. 3

   Inspect the wiring harness and connectors between the FPP sensor and the ECM for corroded pins, chafed wires, or loose connections.

4. 4

   Verify that the system battery voltage is healthy (typically between 9.0V and 16.0V) to ensure stable 5V reference signals.

1. 1

   Disconnect Power

   Turn off the equipment key switch and disconnect the negative battery cable to prevent electrical shorts during repair.

2. 2

   Access the Sensor

   Locate the Foot Pedal Position sensor, which is generally integrated directly into the foot pedal mechanism mounted on the operator's platform.

3. 3

   Test the Circuit

   Disconnect the electrical connector at the pedal. Using a multimeter, check for continuity on the signal, 5V reference, and ground circuits between the pedal connector and the ECM harness.

4. 4

   Repair Wiring (If Applicable)

   If an open or short circuit is found in the harness, repair the damaged section of the wire or replace the connector pigtail.

5. 5

   Replace the Sensor

   If the wiring tests perfectly, the internal potentiometers of the FPP sensor have failed. Unbolt the accelerator pedal assembly/sensor from the floorboard and install a new unit.

6. 6

   Reassemble and Clear Codes

   Reconnect the sensor and the battery. Turn the key to the ON position (engine off) and use your diagnostic tool to clear the P2126 code.

7. 7

   Verification Test

   Depress the pedal fully and release it while watching live data to ensure FPP1 and FPP2 now match. Start the engine and verify that the MIL remains off and the engine operates without power deration.