Kubota P0221 – Engine Control Module (ECM / ECU): TPS1 % Higher Than TPS2 %

This code indicates a plausibility error within the Throttle Position Sensor (TPS). The ECU continuously compares the percentage values of both sensors (TPS1 and TPS2) and triggers this code when the engine is running and the difference between TPS1 and TPS2 is out of the acceptable range (< -20.0% or > 20.0%) for at least 1 second. The system will typically initiate an engine shutdown or force the machine into a severe limp mode to prevent runaway acceleration.

• Kubota WG1605
• Kubota WG2503
• Kubota RTV-XG850 Sidekick
• Haulotte HA16RTJ Pro
• Haulotte HA26 RTJ Pro

1. 1

   Scan for associated throttle codes such as P0121, P2112, or 5V reference codes

2. 2

   Inspect the wiring harness leading to the Throttle Position Sensor and Throttle Body for chafed wires, melted insulation, or a loose connector

3. 3

   Disconnect the TPS and inspect the 6-pin connector for water intrusion, corrosion, or pushed-out pins

4. 4

   Using a diagnostic scanner, monitor live data for both TPS1 and TPS2 percentages while slowly depressing the accelerator pedal to ensure values track smoothly together without dropouts, spikes, or dead spots

5. 5

   Verify that the sensor is receiving a steady 5V reference and a solid ground from the ECU

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the negative battery cable to prevent electrical shorts and reset the ECU.

2. 2

   Locate the TPS

   Locate the Throttle Position Sensor. Depending on the engine model, it will either be mounted directly on the side of the throttle body (e.g., WG1605/WG2503) or on the accelerator pedal assembly.

3. 3

   Remove the Component

   Disconnect the electrical harness from the sensor and remove the mounting screws. Note: On many modern Kubota engines (like the WG series), the TPS is integrated into the Throttle Body and is not serviced separately; the entire Throttle Body must be replaced.

4. 4

   Install the New Part

   Mount the new TPS or Throttle Body assembly and tighten the fasteners to OEM torque specifications.

5. 5

   Reconnect

   Plug the electrical connector back in and reconnect the battery.

6. 6

   Calibration/Relearn

   Turn the key to the ON position (engine off). Some electronic throttle bodies require a TPS relearn or calibration procedure via a diagnostic scan tool so the ECU can learn the new 0% and 100% throttle plate positions.

7. 7

   Clear Codes and Test

   Clear the P0221 fault code with a scanner and test-run the engine to ensure the code does not return and the machine does not shut down.