Walker 350-34378 Oxygen Sensor - Downstream

Walker 350-34378 Oxygen Sensor Overview

Walker Products 350-34378 is a heated, specific-fit oxygen sensor engineered as an OE-style replacement for downstream monitoring. It is built for vehicles that rely on accurate exhaust feedback to help the ECU manage fuel delivery and emissions performance.

Compatible With 1996-1998 Mercury Villager, downstream and 1996-1997 Nissan Quest, downstream, this Walker Products Aftermarket sensor is a direct-fit option for the listed applications. The 350-34378 part number is designed around the specified mounting position, connector style, and harness layout for a precise replacement.

Key Features

• Heated oxygen sensor for downstream placement
• Specific fit for the listed vehicle applications
• 4-wire design with 20-gauge wiring
• Female connector with radiused polygon shape
• Threaded mounting type with 18.0 mm thread diameter
• 48.35 in. wiring harness length and 51.89 in. overall length

Detailed Description

Walker Products 350-34378 is part of the Walker Products Aftermarket engine management and oxygen sensor line, developed as an OE replacement for many vehicle platforms worldwide. For 1996-1998 Mercury Villager and 1996-1997 Nissan Quest models in the downstream position, this sensor provides the diagnostic feedback the ECU expects from the exhaust system. The heated design helps the sensor reach operating temperature efficiently, supporting stable signal output during normal driving conditions. If your vehicle has stored a fault code related to the oxygen sensor circuit or downstream emissions monitoring, this part number is built for the listed application and connector configuration.

Walker Products has supplied engine management and fuel system components since 1946 and operates under Automotive ISO9001/TS 16949 quality systems. The 350-34378 oxygen sensor reflects that application-specific approach, with fitment, connector, and harness details matched to the vehicle platform.

What This Sensor Helps Address

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

Installation Notes and Tips

Confirm the downstream location before installation and compare the connector shape, wire count, and thread diameter to the original sensor. Inspect the sensor wiring harness and connector for heat damage, abrasion, or corrosion before replacement. The threaded mounting design should be installed to the vehicle’s specified torque procedure and with care to avoid cross-threading.

This part cross-references Walker Products Aftermarket 350-34378 for the same application.

Quality Assurance

Walker Products manufactures this oxygen sensor as a specific application replacement with OE-style fitment and ECU feedback requirements in mind. The brand’s ISO9001/TS 16949 quality framework supports consistent production for engine management sensors and related components.