Kubota P1165 – Engine Control Module (ECM) / Engine ECU: Catalyst inactive on LPG

This fault code indicates that the catalytic converter is not operating at the required efficiency threshold while the engine is running on Liquefied Petroleum Gas (LPG).

• Kubota WG1605
• Kubota WG1605-L-E3
• Kubota WG1605-GL-E3
• Kubota WG-972
• Kubota D1105-E3B
• JLG 340AJ
• Haulotte HA16RTJ Pro

1. 1

   Check for exhaust leaks upstream of or near the HEGO (Heated Exhaust Gas Oxygen) sensors, as unmetered oxygen will skew readings.

2. 2

   Check the LPG fuel supply pressure to the gaseous fuel control system to ensure it is not too high or too low.

3. 3

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

4. 4

   Use a diagnostic scan tool to monitor the HEGO sensors. Ensure they are responsive and that the post-catalyst signal circuit is not shorted to the pre-catalyst signal.

5. 5

   Visually inspect the catalytic converter for physical damage, rattling (broken substrate), or contamination.

1. 1

   Fix leaks

   Repair any exhaust leaks, intake manifold leaks, or fuel supply leaks discovered during the diagnostic phase. Replace gaskets as necessary.

2. 2

   Correct fuel pressure

   If the LPG fuel pressure was out of specification, adjust or replace the LPG fuel pressure regulator and verify the fuel filters are clean.

3. 3

   Replace faulty sensors

   If the HEGO sensors are lazy, non-responsive, or shorted, replace the affected O2 sensors.

4. 4

   Replace the catalytic converter

   If the fuel system, exhaust integrity, and sensors all test perfectly, the catalyst element is physically damaged or contaminated. Remove the old catalytic converter/exhaust manifold assembly and install a new one.

5. 5

   Clear and verify

   Clear the P1165 fault code from the ECM. Run the engine on LPG until it reaches operating temperature and operate it under load to allow the ECM to run the catalyst monitor and verify the repair.