Kubota P1162 – Engine Control Module (ECM): Adaptive Learn Low (LPG)

The engine control system has detected a rich air/fuel condition and has reached its negative adaptive learning limit while trying to compensate. Specifically, the code triggers when the engine is running in Adaptive Mode and the Adaptive Learn Bank Multiplier (AL_BM) drops below -30% for at least 3 consecutive updates.

• Kubota WG-series
• WG1605
• WG2403
• WG2503
• WG3800
• Haulotte HA16RTJ Pro
• Snorkel TB60
• Forklifts
• Industrial sweepers
• Portable heaters

1. 1

   Check Live Data: Connect a diagnostic scan tool and monitor the Adaptive Learn Bank Multiplier (AL_BM). Confirm that the value is stuck below -30%.

2. 2

   Test LPG Fuel Pressure: Check the fuel supply pressure to the gaseous fuel control system. Abnormally high fuel pressure is a primary cause of this code.

3. 3

   Inspect the HEGO Sensor: Monitor the Heated Exhaust Gas Oxygen (HEGO) sensor voltage to see if it is non-responsive or sluggish.

4. 4

   Check for Exhaust Leaks: Visually and audibly inspect the exhaust system for leaks upstream of or near the HEGO sensor, which can skew oxygen readings and force the ECM to overcompensate.

1. 1

   Scan and Verify

   Connect your diagnostic tool, read all stored DTCs, and record the freeze-frame data to verify the conditions under which P1162 was set.

2. 2

   Inspect the Exhaust System

   Check the exhaust manifold and piping near the HEGO sensor for leaks. If leaks are found, replace the affected exhaust gaskets or pipes.

3. 3

   Test the LPG Pressure Regulator

   Connect a pressure gauge to the LPG fuel system. If the pressure regulator/vaporizer is delivering high fuel pressure or is internally faulty, replace the regulator.

4. 4

   Test/Replace the HEGO Sensor

   If the fuel pressure is within specification and there are no exhaust leaks, the HEGO sensor is likely non-responsive. Replace the HEGO sensor. (Note: When installing a new HEGO sensor, avoid using silicone-based sealers or lubricants, as silicone will contaminate and ruin the new sensor).

5. 5

   Clear Codes and Test

   Clear the DTCs using the scan tool. Run the engine until it reaches operating temperature and enters Closed Loop mode. Verify that the AL_BM parameter returns to a normal operating range (between -30% and +30%).