Open Loop
WARNING: This page is about a different car, the 1996 Acura SLX. 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 500 RPM, ECM operates in open loop mode. In open loop, ECM calculates air/fuel ratio based upon coolant temperature and Manifold Absolute Pressure (MAP) sensor readings. Engine remains in open loop operation until O2S reaches operating temperature, coolant temperature reaches preset temperature and a specific period of time has elapsed after engine starts.