Kubota P1164 – Engine Control Unit (ECU): Adaptive Learn Low (NG)

The engine's fuel trim (adaptive learning) has reached its maximum lower limit while operating on Natural Gas (NG). The engine is running too rich, and the system is attempting to pull away as much fuel as possible but cannot compensate any further. This is primarily caused by abnormally high fuel pressure from a faulty fuel pressure regulator, or a non-responsive HEGO sensor.

• WG Series
• WG972
• WG1605
• WG3800
• DG series

1. 1

   Verify Operating Conditions: Ensure the engine is reaching operating temperature and running in Closed Loop Mode (CL_BM > 35%).

2. 2

   Test Fuel Pressure: Connect a pressure gauge to the natural gas fuel supply line. Check if the pressure is excessively high, which points directly to a failed regulator.

3. 3

   Monitor the HEGO Sensor: Use a diagnostic scan tool to watch the O2 sensor data. Confirm whether the sensor is switching properly or if it is non-responsive/stuck reading rich.

4. 4

   Inspect for Exhaust Leaks: Check for any exhaust leaks upstream of or near the HEGO sensor, as this can skew the sensor's readings and force the ECU into a false adaptive learn state.

1. 1

   Relieve System Pressure

   Safely shut off the natural gas supply and relieve the fuel system pressure before opening any lines.

2. 2

   Replace Faulty Components

   If the fuel pressure tested too high, remove and replace the natural gas fuel pressure regulator. If the HEGO sensor was non-responsive during diagnostic monitoring, replace the O2 sensor.

3. 3

   Check for Leaks

   After installing the new regulator or sensor, turn the gas supply back on and use a gas leak detector solution on all disturbed fittings to ensure there are no leaks.

4. 4

   Clear the Code

   Connect your diagnostic tool to the ECU and clear the P1164 code. (Note: The code should only be cleared after the mechanical repair is made).

5. 5

   Test Run

   Start the engine, allow it to reach operating temperature so it enters Closed Loop mode, and verify that the engine operates smoothly without triggering a power derate or logging the code again.