O2 Oxygen Sensor Upstream Downstream for Subaru Impreza, Forester, Legacy, Outback (2006-2009) 2.5L

Direct-Fit O2 Oxygen Sensor Set for 2006-2009 Subaru Impreza, Forester, Legacy, Outback (GD, SG, BL, BP)

What it Does: The Upstream and Downstream O2 Sensor Set replaces degraded exhaust gas sensors on 2006-2009 Subaru 2.5L vehicles to restore factory air-fuel closed-loop feedback, resolve diagnostic trouble codes, and stabilize idle trim.

The Stock Subaru Impreza, Forester, Legacy, Outback Sensor Contamination and Thermal Fatigue

Over extended thermal cycles, the factory zirconia ceramic sensing elements in the EJ253 exhaust stream suffer severe silica, carbon, and oil vapor contamination. On chassis platforms like the GD/GE Impreza, SG/SH Forester, and BL/BP Legacy/Outback, aging upstream air-fuel ratio sensors (A/F) exhibit signal latency and drifted output voltage. This latency forces the ECM into rich or lean bias, causing catalyst inefficiency codes (P0420, P0430), circuit faults (P0130 through P0161), catalytic converter damage, rough cold idle, and elevated hydrocarbon emissions.

The Engineering Solution

Engineered to precise OEM specifications, this complete pre- and post-catalyst sensor pair features double-protection stainless steel housings that resist exhaust gas particulate erosion and thermal shock. The high-speed ceramic sensing elements deliver rapid response times, allowing the factory ECU to dynamically regulate stoichiometric fueling (14.7:1 AFR) across all load ranges. Pre-crimped harness terminals, factory-matched wiring loom lengths, and OEM waterproof connectors guarantee plug-and-play installation into factory bungs without wire slicing, terminal pinning, or resistance errors.

What's Included

• 1 Upstream Oxygen (A/F) Sensor
• 1 Downstream Oxygen Sensor

Technical Specifications

Compatibility

• 2006-2009 Subaru Impreza 2.5L (Naturally Aspirated)
• 2006-2009 Subaru Forester 2.5L (Naturally Aspirated)
• 2006-2009 Subaru Legacy 2.5L (Naturally Aspirated)
• 2006-2009 Subaru Outback 2.5L (Naturally Aspirated)

Frequently Asked Questions & Fitment Warnings

Does this fit the BL/BP, SG/SH, and GD/GE Impreza, Forester, Legacy, Outback?

Yes, this is a direct fit for 2006-2009 models equipped with the naturally aspirated EJ253 2.5L engine; it does not fit turbocharged EJ255 or EJ257 models.

Should anti-seize be applied during installation?

Apply high-temperature anti-seize sparingly to the sensor threads only, ensuring none touches the protective perforated sensing tip to prevent immediate element contamination.

The Subaru Boxer Calibration Standard

Preserve boxer engine response, restore closed-loop fuel economy, and eliminate persistent CEL indicators with exact-voltage feedback engineered for naturally aspirated EJ-series performance.