Kubota P1171 – Engine Control Module (ECM): EPR/CFV Regulation Pressure Higher than Expected

The Engine Control Module has detected that the inlet fuel pressure to the DEPR (Direct Electronic Pressure Regulator) is too high. When this fault is triggered, the system will disable Closed Loop (CL) fuel control and Adaptive Learn (AL) functions, and it will illuminate the Engine Warning Light (MIL).

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• WG1605-N-E3
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• WG1605-GLN-E3
• WG2503
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• Allen Engineering riding trowels

1. 1

   Connect a diagnostic scan tool to read live data and monitor the DEPR inlet pressure to see if it is genuinely high or reading erratically.

2. 2

   Use a mechanical pressure gauge to verify the actual output pressure of the Dual Stage Regulator (DSR) to check for mechanical failure feeding excessive pressure.

3. 3

   Check the DEPR 4-pin harness (Power, Ground, CAN High, CAN Low) for shorts to power that could cause a false high-pressure reading.

4. 4

   Ensure the 12-volt LPG fuel lock-off solenoid is operating correctly and not sticking open or closed.

1. 1

   Safety First

   Close the manual fuel valve at the LPG/NG tank. Run the engine until it stalls to safely bleed the pressurized fuel from the lines. Disconnect the negative battery cable.

2. 2

   Isolate the Fault

   Based on your mechanical gauge test, determine if the high pressure is a mechanical failure of the DSR (feeding too much pressure) or an electronic failure of the DEPR (reading pressure incorrectly).

3. 3

   Replace DSR (if mechanical overpressure)

   Clamp off the coolant hoses running to the DSR vaporizer to minimize coolant loss. Disconnect the fuel inlet and outlet lines from the DSR. Unbolt the DSR from its mounting bracket and install the new unit. Reconnect the fuel lines and coolant hoses. Top off the engine coolant.

4. 4

   Replace DEPR (if sensor/electronic failure)

   Disconnect the 4-pin electrical connector from the DEPR. Disconnect the fuel inlet hose (coming from the DSR) and the outlet hose (going to the mixer). Remove the mounting hardware and replace the DEPR assembly.

5. 5

   Reassembly and Testing

   Reconnect the battery. Slowly open the manual valve at the fuel tank. Use a gas leak detector or soapy water solution to check all disturbed fittings for leaks. Connect the diagnostic tool, clear DTC 1171, and start the engine. Monitor the DEPR pressure live data to ensure it remains within the expected parameters.