O2 Oxygen Sensor Upstream Downstream for Subaru Crosstrek Impreza (2016-2020) 2.0L

Direct-Fit Upstream & Downstream O2 Sensor Kit for 2016-2020 Subaru Crosstrek & Impreza (GP/GT/GJ/GK)

What it Does: This matched upstream and downstream oxygen sensor kit monitors exhaust oxygen levels on the FB20 2.0L H4 in GP/GT/GJ/GK Subaru Crosstrek and Impreza models to regulate air-fuel ratio and catalyst efficiency.

The Stock Subaru Crosstrek & Impreza O2 Sensor Failure

On GP/GT/GJ/GK vehicles equipped with the FB20 2.0L H4, factory upstream and downstream oxygen sensors suffer from thermal cycling fatigue, silicone or oil-vapor contamination, and internal heater circuit burnout. Once the zirconia element slows or the heater opens, the ECM loses accurate closed-loop lambda feedback. This degradation forces incorrect fuel trims and triggers P0137, P0171, P0030, or P0420 fault codes.

Common Symptoms of a Failing OEM Oxygen Sensor

• Check Engine Light: Triggers P0137, P0030, P0171, or P0420 from sluggish switching or heater faults.
• Erratic Fuel Trims: Skewed lambda readings cause rough idle and hesitation under load.
• Poor Economy & Emissions: Rich running reduces MPG and blocks emissions readiness.

The Direct-Fit Zirconia O2 Sensor Solution

Engineered as direct-fit replacements for OEM numbers 234-9138 and 22641-AA670, this matched kit pairs a fast-acting upstream air-fuel sensor with a precision downstream zirconia narrowband sensor. Laser-welded stainless steel housings, PTFE breathability filters, and dual-layer protective shields resist moisture shock and carbon fouling. Factory-length harnesses and keyed OEM connectors bolt directly into stock exhaust bungs without splicing.

What's Included

• 1 Upstream Oxygen Sensor
• 1 Downstream Oxygen Sensor

Technical Specifications

Compatibility

• Crosstrek 2016-2020 2.0L Naturally Aspirated (Hybrid and Plug-In Hybrid not included)
• Impreza 2016-2017 2.0L

Frequently Asked Questions & Fitment Warnings

Does this fit the GP/GT/GJ/GK Crosstrek & Impreza?

Yes. Fits 2016-2020 Crosstrek and 2016-2017 Impreza with the naturally aspirated FB20 2.0L H4. Excludes hybrid and plug-in hybrid trims; confirm engine before ordering.

Will this clear P0137, P0171, or P0420 codes?

Yes, if worn sensors caused the fault. Replacing 234-9138 and 22641-AA670 restores lambda accuracy; inspect for exhaust leaks if P0420 persists.

Are OEM connectors included for direct installation?

Yes. Both sensors feature factory-keyed plugs and OEM thread pitch; tighten to spec without contaminating sensor tips.

The Subaru Precision Standard

Built for accurate closed-loop fueling on the FB20 2.0L H4, this sensor kit restores crisp throttle response and CEL-free emissions compliance. High-temperature durability ensures steady voltage output across daily driving.