Kubota P0628 – Engine Control Module (ECM) / Engine ECU: Fuel Pump Relay Ground Short (Gas/LPG) / SCV Drive System Abnormality Ground Short (Diesel)

For Gas/LPG engines, the ECM detects that the fuel pump relay coil output is shorted to ground for more than 10 samples of the circuit. For Common Rail Diesel engines, the ECM detects a ground short circuit in the Suction Control Valve (SCV / MPROP) on the high-pressure fuel pump, resulting in insufficient fuel output and an automatic engine stop.

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1. 1

   For Gas/LPG engines: Verify the enabling conditions (Key On, Engine Off).

2. 2

   For Gas/LPG engines: Check the fuel pump relay pull-in coil to see if it is shorted internally.

3. 3

   For Gas/LPG engines: Inspect the relay driver circuit in the engine wiring harness for a short to ground.

4. 4

   For Gas/LPG engines: Check the fuel pump and pressure sensor wiring for damage or exposed wires.

5. 5

   For Diesel engines: Inspect the SCV solenoid on the HP3 supply pump for internal shorts.

6. 6

   For Diesel engines: Check the wiring harness connecting the SCV to the Engine ECU for ground shorts or chafing.

1. 1

   Turn ignition ON

   For Gas/LPG: Turn the ignition key to the ON position with the engine OFF.

2. 2

   Locate fuel pump relay

   For Gas/LPG: Locate the fuel pump relay in the main fuse/relay box.

3. 3

   Test and replace relay

   For Gas/LPG: Remove the relay and test the pull-in coil resistance with a multimeter. If the coil is shorted internally, replace the relay.

4. 4

   Trace relay driver circuit

   For Gas/LPG: If the relay tests good, use a multimeter to trace the relay driver circuit wiring harness back to the ECM. Look for continuity to ground where there shouldn't be any.

5. 5

   Repair wiring harness

   For Gas/LPG: Repair or replace any damaged sections of the wiring harness.

6. 6

   Replace or reprogram ECM

   For Gas/LPG: If the relay and wiring harness are both in good working order, the ECM itself may be faulty and require replacement or reprogramming.

7. 7

   Locate SCV

   For Diesel: Locate the Suction Control Valve (SCV) on the high-pressure fuel supply pump.

8. 8

   Test SCV wiring harness

   For Diesel: Disconnect the SCV electrical connector and test the wiring harness back to the ECU for a short to ground. Repair the harness if a short is found.

9. 9

   Replace SCV

   For Diesel: If the wiring is intact, the SCV solenoid has failed internally and the SCV must be replaced.