Open Loop Mode
WARNING: This page does not describe the selected car, but rather 33 other vehicles, including the 2002 Saturn Vue, 2002 Pontiac Montana, 2002 Pontiac Aztek, 2002 Oldsmobile Silhouette, and 2002 Oldsmobile Bravada. However, it is still accessible from the selected car via links, so may be relevant.
When engine is cold and engine speed is greater than 400 RPM, PCM operates in open loop mode. In open loop mode, PCM 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.