Yale 522655-1 – Engine Control Unit (ECU): Short Term Closed Loop Correction Bank 1 Greater Than NOR 35% (or 40%) (Lean Engine Operation)

The engine is running too lean (too much air, not enough fuel). The system uses an oxygen (O2) sensor to monitor the exhaust; when it detects a lean condition, the ECU attempts to correct it by adding fuel. This fault code is triggered when the ECU has reached its maximum allowable short-term fuel trim adjustment (greater than 35% or 40% above normal) and the engine is still running lean.

• Yale and Hyster Forklifts
• Yale GLC030
• Yale GLP050
• Yale GLP040-155VX
• Yale GLP40-60MX
• Hyster S50FT
• Hyster H35FT
• Hyster H40FT
• Hyster H60FT
• Hyster H70FT
• Hyster Fortis 60
• Hyster S120FTPRS

1. 1

   Check the air filter for severe clogs and inspect the LPG fuel filters (primary and inside the regulator) for contamination

2. 2

   Check for low primary LPG fuel pressure (feeding the trim fuel injector) and low secondary LPG fuel pressure (feeding the carburetor/mixer)

3. 3

   Inspect the intake manifold for vacuum leaks and the exhaust system for leaks prior to or near the oxygen (O2) sensors

4. 4

   Monitor the pre-cat and post-cat O2 sensors to see if they read incorrectly once the engine heats up

5. 5

   Inspect the LPG regulator/vaporizer and the EPR (Electronic Pressure Regulator)/mixer for tar buildup, worn diaphragms, or freezing

6. 6

   Check the trim fuel injector and its wiring for faults, clogs, or contamination

1. 1

   Clear and Test

   Clear the fault code and operate the forklift normally. Sometimes this code triggers simply because the engine has idled for too long. If it returns during normal operation under load, proceed to mechanical repairs.

2. 2

   Filter Maintenance

   Replace the air filter if it is dirty or has been blown out too many times. Replace the primary LPG fuel filter.

3. 3

   Address Leaks

   Seal any discovered vacuum leaks at the intake manifold or exhaust leaks near the O2 sensors.

4. 4

   Clean/Rebuild the Regulator

   Drain any tar buildup from the vaporizer/EPR system. If the regulator diaphragm is worn or leaking, rebuild it using a repair kit or replace the entire LPG regulator assembly.

5. 5

   Replace O2 Sensors

   If the operator reports a strong smell of propane but the engine runs lean, or if the code only appears after the engine warms up, replace the heated Oxygen (O2) sensors (pre and post-catalytic converter).

6. 6

   Service the Trim Injector

   If the code persists, remove the trim fuel injector. Clean it thoroughly to remove heavy LPG particulates. If it fails to pulse or has a wiring short, replace the injector.