Ford OEM – (Rear) O₂ Sensor for 2016-2018 Focus RS

Ford OEM – (Rear) O₂ Sensor for 2016-2018 Focus RS

If you’ve already addressed upstream O₂ sensor issues from a catless downpipe or exhaust mod, don’t overlook the downstream (secondary) O₂ sensor on your 2016-2018 Focus RS. This sensor sits after the catalytic converter location and still feeds critical oxygen data into the ECU. Without a proper downstream sensor, the ECU can throw faulty AFR readings, random check engine lights, emission codes, and unstable tuning behavior because it’s still expecting a post-cat efficiency signal.

The Ford OEM downstream oxygen sensor (Ford part FB5Z-9G444C and similar OEM variants) is a genuine factory-specified replacement that restores accurate post-convertor oxygen monitoring so your ECU can get reliable post-cat data. Whether you’re on stock exhaust or a fully modified setup, this sensor helps prevent false error codes and keeps your tune running cleanly.

Key Features

• Factory-spec replacement: Genuine OEM rear/secondary oxygen sensor tuned for Focus RS 2.3L EcoBoost post-cat oxygen monitoring.

• Accurate post-cat feedback: Measures exhaust oxygen content after the converter location, allowing your ECU to correctly track emissions and AFR curves.

• Stops false CELs: Helps eliminate check engine lights and downstream O₂-related diagnostic codes caused by incorrect sensor readings.

• Durable OEM quality: Designed to handle hot exhaust environments and long service life at OEM standards.

• Critical for tuned/exhaust mods: Essential when running catless downpipes or performance exhausts to keep ECU logic stable.

Application

Fits downstream (secondary) O₂ sensor position for Ford Focus RS 2016-2018 with 2.3L EcoBoost engines; plug-and-play with factory harness.

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