What does OL mean on fuel system 1?
What does OL mean on fuel system 1? OL = Open loop. When you start the car till it warms up it runs in the Open loop mode. Meaning it will not monitor the O2 sensors till the car engine warms up enough to get into Closed loop mode (i.e. monitor the air/fuel ratio based on the O2 sensor readings) What does FUELSYS1 ol mean? Senior Member. I know what the misfire part means. On all the previous error codes I have been getting P0420 with "FUELSYS1 CL". I have found "OL" means open looped and "CL" means closed looped....