Denso 234-3091 Oxygen Sensor - Upstream

Denso OE Style Oxygen Sensor 234-3091

Denso 234-3091 is an OE-style heated oxygen sensor built for specific-fit Subaru applications. It is engineered for direct replacement on upstream locations in select Subaru Forester, Impreza, and Legacy models, helping restore accurate exhaust feedback for proper fuel control.

For drivers searching for a Subaru Forester oxygen sensor upstream replacement or a Subaru Impreza oxygen sensor OE-style fit, this Denso sensor is built to match the original mounting and connector style for a first-time fit.

Key Features

• Heated oxygen sensor with specific-fit design
• OE-style replacement for direct installation in the original location
• 3-wire configuration with female connector
• Threaded mounting type with 0.708 in. thread diameter
• 17.32 in. wiring harness length for vehicle-specific routing
• Built to strict OE standards with precision construction
• Aluminum oxide trap layer helps protect the ceramic element from silicone and lead contamination

Detailed Description

Denso 234-3091 is designed for upstream exhaust monitoring on 1996-1999 Subaru Legacy, 1998-1999 Subaru Forester, and 1998-1999 Subaru Impreza applications, including 1999 Subaru Impreza Canada & Exc. Calif. and 1999 Subaru Legacy Excluding California. This OE Style oxygen sensor is intended to deliver the correct signal response for engine management systems that rely on accurate air-fuel feedback.

This part cross-references Subaru 22690AA290 and 22690AA350 for the same application. It also aligns with common aftermarket references such as Bosch 13702 and NTK 24523. The Denso 234-3091 is a practical choice when you need a direct-fit Subaru oxygen sensor for upstream service.

What It Helps Address

• Check engine light caused by a failing upstream oxygen sensor
• Rough idle or inconsistent air-fuel readings
• Reduced fuel economy from inaccurate exhaust feedback
• Slow sensor response during closed-loop operation
• Contamination-related sensor degradation from silicone or lead exposure

Installation Notes and Tips

Verify the connector, thread size, and harness length against the original sensor before installation. This is a specific-fit, threaded heated oxygen sensor for upstream placement, so confirm the vehicle year, model, and emissions configuration match the listed Subaru applications. For best results, inspect the harness routing and connector condition during replacement.

Quality Assurance

Denso manufactures and tests this OE Style oxygen sensor to OE-level standards for replacement accuracy and consistent fit. The sensor design includes contamination protection for the sensing element, supporting long service life in demanding exhaust environments.