Kubota P0261 – Engine Control Unit (ECU / ECM): Injector Driver #1 Open/Short-To-Ground

This fault indicates a critical electrical failure in the circuit controlling the fuel injector for cylinder #1. The system has detected a loss of the 12.0V electrical feed to the injector, an open circuit within the injector coil itself, or the injector driver circuit within the engine wiring harness is either open or shorted to ground.

• D1105
• WG972
• WG1605 (G/GL/E3)
• V2403
• V3800
• U50-5
• U56-5
• KX060-5
• Toro mowers
• Carrier generator sets

1. 1

   Check battery voltage to ensure it is above 9.0V, as low voltage can trigger false driver codes.

2. 2

   Visually inspect the engine wiring harness leading to cylinder #1 for chafing, melted insulation, or pinched wires that could cause a short to ground.

3. 3

   Inspect the Engine ECU connectors and the connector at injector #1 for bent pins, moisture, or corrosion.

4. 4

   With the key ON, verify that there is a 12.0V supply reaching the positive side of the injector #1 coil.

5. 5

   Disconnect injector #1 and measure the resistance across its terminals to check for an internal open or shorted coil.

6. 6

   Test the ground/driver wire from the injector connector back to the ECU pin for continuity and ensure it is not shorted to the engine block (ground).

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery terminal to prevent electrical damage during testing.

2. 2

   Isolate the Fault

   Based on the diagnostic checks, determine if the fault lies in the wiring harness, the injector, or the ECU.

3. 3

   Repair Wiring (If Applicable)

   If the harness continuity test reveals an open circuit or a short-to-ground, locate the damaged section of the wiring harness. Splice and repair the wire using weather-sealed connectors, or replace the engine harness section if the damage is extensive.

4. 4

   Replace Injector (If Applicable)

   If the injector coil fails the resistance test (showing an open circuit or internal short), remove the fuel lines and retaining hardware for cylinder #1. Install a new OEM Kubota fuel injector. Note: Gasoline/LPG injectors do not require adjustment, but diesel common rail injectors may require the new injector's QR code to be programmed into the ECU using Diagmaster.

5. 5

   Reassemble and Clear Codes

   Reconnect all electrical connectors and the battery. Connect a diagnostic tool to the machine, clear the P0261 (and associated SPN 651) fault code, and run the engine to verify that the cylinder is firing correctly and the code does not return.