Kubota P0652 – Engine Control Unit (Engine-ECU / ECM): Sensor Supply Voltage 2 Low

The ECU detects that the voltage on the Sensor Supply #2 circuit has dropped below a specified threshold (typically 4.59V, or 4.375V transient). This voltage drop is almost always caused by a short circuit to ground in the wiring harness, a shorted sensor dragging the circuit voltage down, or a failure within the ECU's internal power supply.

• SVL65-2
• SVL75-2
• SVL90-2
• SVL95-2S
• SVL97-2
• SSV65
• SSV75
• KX040-4
• KX057-4
• KX080-4
• U55-4
• M4-series
• M6060
• M7060

1. 1

   Check battery voltage (ensure it is between 8 and 16 volts) to rule out a weak battery or poor main power supply causing false low-voltage readings.

2. 2

   Visually inspect the wiring harness for the 5V reference circuit for any obvious signs of chafing, melted wires, corrosion, or a short to ground.

3. 3

   Perform a sensor isolation test by unplugging sensors sharing the 5V reference circuit one by one while monitoring circuit voltage to identify an internally shorted sensor.

1. 1

   Turn the key switch to the ON position (engine off).

2. 2

   Using a multimeter, measure the voltage at the 5V reference pin on one of the affected sensors (e.g., the camshaft position sensor).

3. 3

   If the voltage reads low (under 4.59V), begin disconnecting the sensors on the "Supply 2" circuit one at a time.

4. 4

   After each disconnection, check the multimeter. If the voltage jumps back up to approximately 5V, the sensor you just disconnected is shorted. Replace that specific sensor.

5. 5

   If disconnecting all sensors does not restore the 5V reference, use a wiring diagram to trace the harness back to the ECU. Test the harness for continuity to ground. If a short to ground is found in the wiring, repair or replace the damaged section of the harness.

6. 6

   If the wiring harness is completely intact and no sensors are shorted, the Engine ECU is failing to output the correct voltage. The Engine ECU will need to be replaced.

7. 7

   After replacing the faulty component, clear the diagnostic trouble codes using a diagnostic tool (like Kubota Diagmaster) and cycle the ignition to ensure the code does not return.