2x Up+Downstream Oxygen Sensor Fit Ford Escape Fusion 2.5L L4 2014-2016 234-5176 Fit for: Ford Ford Escape 2.5L L4 2014-2016 Ford Fusion 2.5L L4 2014-2016 Ford Transit Connect 2.5L L4 2014-2015 Specifications: OE Numbers: 234-5176, 234-4578 Product Material: Stainless Steel Product Color: Silver Installation Position: Upstream, Downstream Functions: 1. The Upstream oxygen sensor is used to Monitor Raw Exhaust Gas to Adjust Air-fuel Ratio in Real-time, i.e., it is used to Detect Whether the Exhaust Gas Exceeds the Standard. .