Heated Oxygen Sensor (HO2S) and Catalyst Monitor Sensor (CMS)

WARNING: This page is about a different car, the 2012 Ford Pickup, 2012 Ford F550 Super Duty, 2012 Ford F450 Super Duty, and 2012 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

The HO2S and CMS:

have the ability to create a voltage signal dependent on exhaust oxygen content.
provide feedback information to the PCM used to calculate fuel delivery.