Open Loop

When engine is cold and engine speed is greater than 400 RPM, PCM/VCM operates in "open loop" mode. In "open loop" mode, PCM/VCM calculates air/fuel ratio based upon coolant temperature and MAP or MAF sensor readings. Engine remains in "open loop" mode until O2S reaches operating temperature, coolant temperature reaches a preset temperature and a specific period of time has elapsed after engine starts.