A-Premium Upstream & Downstream O2 Oxygen Sensor 2‑Pack for Subaru H4 2.0L/2.5L — Heated, Direct-Fit with 425/400mm Cables

A-Premium Upstream & Downstream O2 Oxygen Sensor 2-pack replaces factory oxygen sensors for compatible Subaru models to help restore accurate air-fuel sensing and steady engine performance.

These two heated oxygen sensors are built as direct-fit replacements for a range of Subaru naturally aspirated 4-cylinder engines. Each sensor includes a threaded mounting, a four-wire male connector, and paired cable lengths (425 mm and 400 mm) so installers can reuse the original wiring routing without splicing. Packaged in a box and backed by A-Premium's one-year unlimited-mileage warranty, this set aims to match OEM fit and function while offering low-effort installation.

Which Subaru models and engines work with this oxygen sensor set?

This A-Premium pair is designed for upstream and downstream positions across several Subaru lineups from the early 2010s to 2020. It fits naturally aspirated H4 engines and specific model-year ranges noted for the compatible 2.0L and 2.5L engines. Always verify part reference numbers and connector type against your vehicle before ordering.

• Compatible models include Crosstrek (2013–2020 variants listed), Forester (2013–2020 H4 2.5L NA), Impreza (2012–2020 H4 2.0L), Legacy/Outback (2013–2019 H4 2.5L DOHC)
• Designed for naturally aspirated 2.0L and 2.5L Subaru H4 engines
• Check cross-reference numbers: 350-34052, 250-24487, 250-54084, 350-64031, OS5579

How do these sensors install and what tools are required?

Installation follows standard oxygen sensor replacement steps and typically needs only common hand tools. The threaded mount and male connector match factory positions, and the four-wire heated design fits directly into the vehicle wiring harness. No special calibration is required after physical installation.

• Threaded mounting for direct bolt-in replacement
• Four-wire heated sensor with male connector for plug-and-play fit
• Cable lengths (425 mm and 400 mm) for correct routing without splicing
• Standard oxygen sensor socket and basic wrenches are sufficient

What are the key specifications and quality features of this A-Premium set?

Each kit contains two sensors built to meet durability and performance expectations for on-road use. The sensors are constructed from premium materials, offer a heated element for faster response at cold start, and come boxed as a matched upstream/downstream pair. A-Premium supports the product with a one-year unlimited-mileage guarantee.

• Package includes 2x heated oxygen sensors (upstream and downstream)
• Wire quantity: 4; connector gender: male; mounting: threaded
• Overall cable lengths: 425 mm + 400 mm for proper routing
• Backed by a one-year unlimited-mileage warranty from A-Premium

Will these sensors trigger error codes or require ECU programming?

When the sensors are the correct fit and wired properly, the vehicle ECU recognizes them as standard oxygen sensors and typically does not require programming. If diagnostic trouble codes persist after replacement, standard troubleshooting (connector inspection, harness continuity, or ECU scan) will indicate next steps. Always clear codes and run a short drive cycle to confirm the repair.

• No special ECU programming when matched to the vehicle harness
• Clear codes and perform a drive cycle after installation to verify functionality
• If codes persist, inspect wiring, connectors, and grounding

Who is this for: This A-Premium oxygen sensor 2-pack is aimed at DIY mechanics, independent repair shops, and Subaru owners who need a reliable upstream and downstream replacement for naturally aspirated H4 engines. Choose this set if you want direct-fit sensors with OEM-style connectors, matched cable lengths for clean installation, and the reassurance of a one-year unlimited-mileage warranty.