Heated Oxygen Sensor (HO2S)
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.
Sensor is located in exhaust manifold, and informs ECM of amount of oxygen in exhaust gases. By heating up HO2S, it can send accurate information before a standard O2S would.