A-Premium Upstream & Downstream Oxygen Sensor Kit for Subaru H4 — Pair, 4‑Wire Heated Direct-Fit

A-Premium Upstream & Downstream O2 Oxygen Sensor kit replaces faulty oxygen sensors on compatible Subaru H4 engines for accurate air/fuel monitoring and restored engine performance.

This pair of heated oxygen sensors (upstream and downstream) is made to fit a range of Subaru models with H4 engines. Designed as a direct-fit replacement, the sensors include a threaded mount, 4-wire heated connectors, and factory-style lengths for plug-and-play installation. Each kit contains two boxed sensors and is backed by A-Premium’s one-year unlimited-mileage guarantee.

Which Subaru models and engines are these sensors compatible with?

The A-Premium sensors are engineered for multiple Subaru applications across model years where the listed engine types were used. They cover both upstream (pre-catalytic converter) and downstream (post-catalytic converter) positions for accurate exhaust monitoring.

• Subaru Crosstrek 2016–2020 H4 2.0L
• Subaru Forester 2013–2020 H4 2.5L (naturally aspirated)
• Subaru Impreza 2012–2020 H4 2.0L
• Subaru Legacy and Outback 2013–2019 H4 2.5L (DOHC)
• XV Crosstrek 2013 / 2014 / 2015 H4 2.0L (GAS where listed)

What are the technical details and reference numbers I should match?

These sensors are 4-wire heated units with male connectors and threaded mounting, supplied as a two-piece boxed set. Use the listed part references to confirm fit with your vehicle’s existing sensor numbers.

• Wire count: 4 (heated sensor)
• Overall cable lengths: approximately 425 mm and 400 mm
• Connector gender: male; mounting: threaded
• Reference numbers: 350-34052, 250-24487, 250-54084, 350-64031, OS5579

How straightforward is installation, and what tools are required?

Installation is intended to be simple for anyone familiar with basic automotive maintenance. The sensors are direct-fit replacements that typically require only common hand tools — no special programming or custom wiring is necessary for most installations.

• Standard oxygen sensor socket or wrench recommended
• Hand tools: ratchet and extensions for access
• No soldering or splicing needed when matching factory connectors
• Allow engine cooldown before removing old sensors for safety

What durability and warranty support does A-Premium provide?

These oxygen sensors are built from durable materials to withstand exhaust conditions and provide consistent readings. A-Premium backs the sensors with a one-year unlimited-mileage guarantee to cover functional defects, giving added confidence after purchase.

• Constructed from premium materials for long service life
• Packaged as two boxed sensors for upstream and downstream positions
• One-year unlimited-mileage warranty included
• Sold as a matched pair for consistent system performance

Who is this for: This A-Premium O2 sensor kit is intended for Subaru owners, independent mechanics, and DIY enthusiasts who need a reliable upstream and downstream replacement for affected Crosstrek, Forester, Impreza, Legacy, Outback, or XV models. It suits anyone seeking a cost-effective, direct-fit sensor pair that restores proper exhaust sensing without custom modifications.