O2 Oxygen Sensor Upstream Downstream for Ford Fusion (2017-2020) 2.5L

Direct-Fit Upstream & Downstream O2 Oxygen Sensor Kit for 2017-2020 Ford Fusion (CD4)

What it Does: This matched upstream (Bank 1 Sensor 1) and downstream (Bank 1 Sensor 2) oxygen sensor kit restores closed-loop air-fuel metering and catalyst monitoring on the 2017-2020 Ford Fusion CD4 with the 2.5L Duratec I4 engine.

The Stock Ford Fusion Sensor Failure

Over high mileage on the CD4 chassis, factory Bank 1 Sensor 1 and Sensor 2 units on the 2.5L Duratec I4 suffer thermal fatigue, heater circuit burnout, and zirconia contamination. Carbon fouling slows voltage switching between rich and lean states, disrupting PCM fuel trim control. This degradation triggers fault codes including P0133, P0135, P0141, and P0171.

Common Symptoms of a Failing OEM Oxygen Sensor

• Check Engine Light / DTCs: Triggers codes like P0133, P0135, or P0141 from slow switching or heater circuit failure.
• Poor Fuel Economy & Idle: Sluggish upstream feedback forces rich fueling, rough idle, and reduced MPG.
• Failed Emissions Testing: Faulty downstream data blocks readiness monitors and causes false catalyst efficiency faults.

The Direct-Fit Oxygen Sensors Solution

Built to replace OEM numbers 250-25135 (25025135) and 250-241226 (250241226), this matched kit pairs fast-light-off zirconia sensing elements with stainless-steel shields. Laser-welded housings resist exhaust condensation shock, while factory-length harnesses and weather-sealed connectors plug directly into the CD4 loom. Replacing both sensors together restores balanced air-fuel feedback and catalyst monitoring without cutting or splicing.

What's Included

• 1 Upstream Oxygen Sensor (Bank 1 Sensor 1)
• 1 Downstream Oxygen Sensor (Bank 1 Sensor 2)

Technical Specifications

Compatibility

• 2017-2020 Ford Fusion — 2.5L Gas I4 (1 Upstream Bank 1 Sensor 1 & 1 Downstream Bank 1 Sensor 2)
• Exclusions: Does NOT fit Hybrid models; 2013-2016 models are not covered in this listing.

Frequently Asked Questions & Fitment Warnings

Does this fit the CD4 Fusion?

Yes. This is a direct fit for the 2017-2020 Ford Fusion equipped with the 2.5L Duratec I4 gasoline engine. Excludes Hybrid models and 2013-2016 applications; confirm engine before ordering.

Will this clear P0135, P0141, or P0133 codes, and are both sensors included?

Yes. Replacing failed sensors resolves P0133, P0135, and P0141 faults after a completed drive cycle, and both Bank 1 Sensor 1 and Bank 1 Sensor 2 are included.

Are factory connectors included for direct installation?

Yes. Both sensors include OEM-style plug-and-play connectors requiring zero splicing; inspect and chase M18x1.5 exhaust bung threads before torquing sensors to spec.

The Ford Precision Standard

Restoring closed-loop fueling on your CD4 Fusion keeps the 2.5L Duratec I4 operating at factory stoichiometry and emissions compliance. Precision connectors and thermal durability ensure reliable, CEL-free operation.