Kubota P1152 – Engine Control Module (ECM): Closed Loop Low (LPG)

This code indicates that the engine is operating in closed-loop mode on Liquefied Petroleum Gas (LPG), but the system is detecting a persistent lean condition (low fuel). The engine control system is attempting to add fuel (Closed Loop Multiplier > 35%), but the oxygen sensor is still reading lean. This triggers a Power Derate level 2.

• Kubota WG1605-E3 engines
• Kubota WG-LSI engines
• Kubota G424FE LP/Dual Fuel engines
• Genie lifts and industrial/agricultural equipment utilizing Kubota LPG engines

1. 1

   Check for any exhaust leaks upstream of or immediately near the HEGO sensor, which can introduce outside oxygen and cause a false lean reading.

2. 2

   Measure the fuel supply pressure to the gaseous fuel control system to ensure it is not reduced.

3. 3

   Inspect the intake manifold and LPG fuel supply lines for vacuum leaks or fuel leaks.

4. 4

   Monitor the HEGO sensor data to see if it is non-responsive (lazy).

5. 5

   Check the wiring harness and connectors for the HEGO sensor and LPG fuel pressure regulator for opens, shorts, or physical damage.

1. 1

   Fix Leaks

   If exhaust or intake manifold leaks are found during the diagnostic phase, replace the corresponding gaskets and tighten hardware to spec.

2. 2

   Restore Fuel Pressure

   If LPG fuel pressure is low, inspect the LPG pressure regulator/vaporizer and fuel filters. Service or replace the regulator if it is failing to deliver adequate pressure to the fuel control system.

3. 3

   Repair Wiring

   Repair any damaged sections of the wiring harness or replace corroded connectors leading to the HEGO sensor.

4. 4

   Replace Sensor

   If the wiring is intact, there are no leaks, and fuel pressure is correct, but the HEGO sensor remains non-responsive, replace the HEGO sensor.

5. 5

   Clear and Verify

   Clear the P1152 fault code from the ECM. Run the engine until it reaches operating temperature and enters closed-loop mode to verify the code does not return and the power derate is lifted.