Kubota P1161 – Engine Control Unit (ECU): Adaptive Learn High (LPG)

This code indicates that the engine's fuel control system has reached its maximum adaptive learning limit (typically AL_BM > 30%) while trying to compensate for an abnormal air/fuel mixture in the LPG system. The Engine Control Unit (ECU) is detecting a condition that forces it to continuously adjust the fuel trim to its upper limit.

• Kubota WG1605-E3
• Kubota D1305
• Toro agricultural/grounds equipment
• JLG Boom Lifts 600S
• JLG Boom Lifts 660SJ
• Haulotte Boom Lifts HA16RTJ Pro
• Haulotte Boom Lifts HA26 RTJ Pro
• Crown Forklifts
• Genie Lifts

1. 1

   Check the LPG delivery pressure from the Electronic Pressure Regulator (EPR) / Megajector to the fuel injection system. Ensure it is not higher than the specified OEM range.

2. 2

   Inspect the intake manifold, vacuum lines, and LPG fuel supply lines for any leaks that could introduce unmetered air or vent fuel.

3. 3

   Inspect the exhaust manifold and piping upstream of the HEGO (O2) sensor. An exhaust leak here will pull in oxygen, causing the HEGO sensor to read falsely lean and forcing the ECU to drive the fuel trim high.

4. 4

   Monitor the HEGO sensor voltage using the Kubota Gasoline Service Tool (KGST) or DST-i interface. Verify that the sensor is responsive and toggling correctly.

5. 5

   Check the LPG fuel injectors to ensure none are stuck open and dumping excess fuel into the cylinders.

1. 1

   Connect Diagnostic Tool

   Connect the Kubota DST-i diagnostic interface and open the KGST software to monitor live data (specifically fuel trims, HEGO voltage, and EPR pressure).

2. 2

   Resolve Exhaust/Intake Leaks

   If any intake manifold leaks or exhaust leaks near the oxygen sensor are found during the visual/smoke test, replace the corresponding gaskets or piping.

3. 3

   Adjust or Replace the Regulator

   If the LPG supply pressure is reading too high, attempt to adjust the LPG pressure regulator. If it cannot be brought into spec or the internal diaphragm is ruptured, replace the regulator/EPR.

4. 4

   Replace the HEGO Sensor

   If live data shows the HEGO sensor is flatlined or sluggish to respond to induced rich/lean conditions, remove and replace the HEGO sensor.

5. 5

   Replace Faulty Injectors

   If an injector is found to be stuck open during a leak-down test, depressurize the LPG system and replace the faulty injector.

6. 6

   Clear Codes and Relearn

   Use the diagnostic tool to clear the P1161 fault code. Run the engine at operating temperature so the ECU can establish a new adaptive learn baseline. Verify the code does not return.