Kubota E-1 – Engine ECU: Acceleration sensor (main) trouble

The Engine Control Unit (ECU) is receiving an out-of-range, missing, or erratic electrical signal from the main accelerator position sensor (APS) or throttle position sensor. This sensor converts the physical position of the throttle pedal or hand lever into an electrical voltage signal to dictate engine RPM and fuel delivery. When this signal fails, the machine may experience sluggish acceleration, rough idling, a dead pedal with no throttle response, or it may force the transmission into neutral to prevent erratic movement.

• M7060
• M5091N
• M5101N
• M5660SUH
• M4N-071
• M5N-091
• M5N-111
• M7-132P
• M120
• M108X
• L3301
• L3901
• L4701
• L3240HST
• L4240HST
• L5740HST
• KX033
• KX057
• KX080
• KX91
• KX121
• KX161
• U35
• U45
• U48
• U55
• SSV series

1. 1

   Inspect the wiring harness and the connector at the acceleration sensor for corrosion, frayed wires, or loose connections.

2. 2

   Perform a sensor wire and lever clearance check by turning the key switch OFF, setting the acceleration hand lever to the MAX rpm position, and measuring the clearance between the acceleration lever and the sensor lever. If out of specification, calibrate the adjusting nut.

3. 3

   Verify that the sensor is receiving its 5V reference voltage from the ECU and that the ground circuit is intact. Use a multimeter to check for a smooth voltage sweep (typically 1.05V to 4.4V) as the pedal or lever is moved. Dead spots indicate a failed internal potentiometer or Hall element.

1. 1

2. 2

   Power down machine

   Turn the key switch to the OFF position, stop the engine, and disconnect the negative battery terminal to prevent electrical shorts.

3. 3

   Locate the sensor

   Locate the main acceleration sensor, typically mounted near the throttle linkage assembly or directly on the accelerator pedal bracket.

4. 4

   Disconnect harness

   Unplug the electrical harness connector from the sensor.

5. 5

   Remove sensor

   Remove the mounting bolts or screws holding the sensor in place and detach the sensor lever and wire linkage.

6. 6

   Install new sensor

   Mount the replacement sensor and secure the hardware. Reattach the linkage.

7. 7

   Adjust clearance

   Set the acceleration lever to the MAX rpm position. Measure the clearance between the acceleration lever and the sensor lever. Adjust the adjusting nut until the clearance meets the factory specification outlined in your specific model's workshop manual.

8. 8

   Reconnect and clear codes

   Reconnect the electrical harness and the battery. Turn the key on and verify throttle response. The code may clear itself upon detecting a valid signal, or it may require a manual reset via the dash menu or a dealer diagnostic tool (Diagmaster).