Kubota P2121 – Engine Control Module (ECM): FPP1 Lower Than FPP2

The Engine Control Module (ECM) detects that the voltage difference between the two internal sensor circuits (FPP1 and FPP2) deviates from the standard expected range (specifically, FPP1 reading lower than FPP2) for a set duration (usually 0.5 seconds).

• WG1605-E3 series
• WG1605-G-E3
• WG1605-L-E3
• WG1605-GL-E3
• SVL series
• SVL75
• SVL90
• SVL95
• SVL97
• SSV series
• L-Series
• L3130
• L3540
• M-Series
• RTV-X series

1. 1

   Connect a diagnostic scan tool and read the freeze-frame data. Monitor live data for 'Accelerator POS No.1' (FPP1) and 'Accelerator POS No.2' (FPP2).

2. 2

   Perform a sweep test by slowly depressing and releasing the accelerator pedal. Both voltage signals should change smoothly and linearly without any dropouts, spikes, or stuck values.

3. 3

   Inspect the pedal assembly and the sensor connector for physical damage, water intrusion, corrosion, or pushed-out pins.

4. 4

   With the key ON (engine OFF), backprobe the sensor connector to verify the presence of a steady 5V reference signal and a solid ground from the ECM.

5. 5

   Perform a wiggle test on the wiring harness between the pedal and the ECM while watching the live voltage data to check for intermittent shorts or open circuits.

1. 1

   Preparation

   Turn the ignition switch OFF and disconnect the negative battery cable to prevent electrical shorts and reset the ECM.

2. 2

   Access the Sensor

   Locate the accelerator pedal position sensor mounted on the pedal bracket. Note: On some tractor models (like the L3540), you may need to remove the cover for the shift/cruise control levers or loosen fender bolts to access the sensor housing.

3. 3

   Disconnect

   Unplug the electrical wiring harness connector from the pedal sensor.

4. 4

   Removal

   Remove the mounting screws (often requiring a right-angle Phillips screwdriver or small socket) securing the sensor to the pedal assembly. On some SVL/RTV models, the entire pedal assembly is replaced as one unit.

5. 5

   Installation

   Mount the new sensor or pedal assembly and tighten the fasteners to OEM torque specs.

6. 6

   Reassembly

   Reconnect the electrical harness and reinstall any covers or panels removed during access.

7. 7

   Calibration/Clear Codes

   Reconnect the battery. Turn the key ON, connect your scan tool, clear the P2121 / DTC 2121 fault code, and verify that the FPP1 and FPP2 voltages are now reading within the standard range.