Kubota P0653 – Engine ECU: Sensor Supply Voltage 2 High

Indicates that the 5-volt external sensor supply circuit 2 (5Vext2) is receiving excessive voltage (transiently exceeding 5.40 V to 5.625 V). This is almost always caused by a wiring harness shorted to a 12.0 V power source (+B) or an internal malfunction within the Engine ECU. The machine will enter Limp Home mode (Power Derate 1), restricting engine output to 50-75%, causing faulty starting, poor engine output, worsening exhaust gas emissions, and the engine warning light turning ON.

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1. 1

   Verify preconditions: ensure battery voltage is normal, ignition key switch is ON, and starter switch signal is not activated

2. 2

   Use a multimeter to check the voltage on the Sensor Supply 2 circuit (5VE2) — fault is confirmed if voltage reads higher than 5.40 V

3. 3

   Visually inspect the engine wiring harness for obvious signs of a short circuit to a 12V power source (+B), such as melted insulation, chafing, or bare wires

4. 4

   Inspect the Engine ECU connectors for loose pins, corrosion, or damage

1. 1

   Disconnect Power

   Disconnect the battery to ensure safety while working on the electrical system.

2. 2

   Harness Inspection & Repair

   Trace the wiring harness between the Engine ECU and the sensors on the Sensor Supply 2 circuit. If a short to 12V power is found, repair the damaged section of the harness or replace the entire engine wiring harness.

3. 3

   Connector Repair

   If the wiring harness is intact, check the ECU connectors. If the connectors are damaged or have poor contact, repair or replace the connector terminals.

4. 4

   ECU Replacement

   If the wiring harness and connectors are in good condition and the voltage remains abnormally high, the Engine ECU has an internal malfunction. You must replace the Engine ECU.

5. 5

   Clear Codes

   Reconnect the battery, turn the key switch OFF, then back ON to see if the code recovers and clears.