Walker 350-64021 Oxygen Sensor - Upstream

Walker 350-64021 Oxygen Sensor Overview

Walker Products 350-64021 is a heated upstream oxygen sensor built as a specific-fit OE replacement for select Subaru and Saab applications. It is engineered to provide the ECU with the feedback needed for proper fuel control, emissions monitoring, and fault detection.

For Subaru WRX STI, WRX, Forester, Impreza, Legacy, Outback, Baja, and Saab 9-2X applications, this upstream oxygen sensor is matched to the vehicle’s fitment position and connector style for direct replacement service.

Key Features

• Heated oxygen sensor for upstream placement
• Specific-fit design for application-matched installation
• 4-wire configuration with 20-gauge wiring
• Radiused polygon male connector
• Threaded mounting with 18.0 mm thread diameter
• Wiring harness length: 29.06 in.; overall length: 32.6 in.
• Walker Products Aftermarket line for engine management and oxygen sensor replacement

Product Details

Walker Products 350-64021 is designed for vehicles that require an upstream oxygen sensor to monitor exhaust oxygen content before the catalytic converter. The heated sensor design helps the engine management system reach operating feedback more quickly, supporting accurate air-fuel control and diagnostic reporting. This part number is built for the specified application and position, making it a direct OE-style replacement for Subaru and Saab models listed in the fitment data.

Walker Products Aftermarket focuses on engine management and oxygen/air-fuel sensors developed for OE replacement use. The brand’s application-specific approach helps ensure the sensor, connector, and harness layout align with the vehicle’s original configuration. Part number 350-64021 is also referenced as Walker Products 350-64021 in catalog and search results.

Fits 2021 Subaru WRX STI, upstream. Fits 2015-2020 Subaru WRX STI, upstream. Fits 2015-2016 Subaru WRX, upstream. Fits 2004-2010 Subaru Forester, upstream. Fits 2004-2008 Subaru Impreza, upstream. Fits 2005-2007 Subaru Legacy, upstream. Fits 2005-2007 Subaru Outback, upstream. Fits 2005 Subaru Baja, upstream. Fits 2006 Saab 9-2X, upstream.

What It Helps Address

• Check engine light related to upstream oxygen sensor faults
• Poor fuel economy caused by incorrect air-fuel feedback
• Rough engine operation from inaccurate exhaust oxygen readings
• Elevated exhaust emissions from a failing sensor
• Stored ECU fault codes tied to the sensor circuit or related systems

Installation Notes

Before replacement, inspect the sensor wiring harness and connector for heat damage, abrasion, or corrosion. Confirm the upstream mounting location and thread size match the original part, and verify the connector shape and wire count before installation. If the vehicle has stored diagnostic trouble codes, clear them after repair and confirm the ECU returns to normal feedback operation.

Quality Assurance

Walker Products manufactures engine management sensors as OE replacement parts for global vehicle applications and operates under Automotive ISO9001/TS 16949 certification standards. Part number 350-64021 is built to the specified fitment and diagnostic requirements for the listed Subaru and Saab applications.