Walker 350-34140 Oxygen Sensor - Downstream or Upstream

Walker 350-34140 Oxygen Sensor Overview

Walker Products 350-34140 is a specific-fit heated oxygen sensor built for direct replacement use in emission control systems. It is engineered for ECU feedback on the listed Mazda applications, helping maintain proper air-fuel monitoring and exhaust system performance.

Walker Products Aftermarket focuses on engine management and oxygen/air-fuel sensors for OE-style replacement needs. The 350-34140 is application-specific, with the correct mounting position, connector style, and wiring configuration for the vehicles listed below.

Key Features

• Heated oxygen sensor for faster operating temperature and signal response
• Specific-fit design for the listed Mazda applications
• 4-wire configuration with 20-gauge wiring
• 29.45 in. wiring harness length and 32.99 in. overall length
• 18.0 mm thread diameter with threaded mounting type
• Male connector with radiused polygon connector shape

Fitment Details

• Fits 2005 Mazda 6, downstream oxygen sensor for B1S2 position in California emissions.
• Fits 2005 Mazda 6, downstream oxygen sensor compatible with California-ESV vehicles in bank 1 position 2.
• Fits 1996-1998 Mazda MPV, upstream oxygen sensor.

Detailed Description

The Walker Products 350-34140 oxygen sensor is built for emission control service where accurate exhaust feedback matters. On the 2005 Mazda 6, it serves the downstream B1S2 position for California emissions and California-ESV configurations. On the 1996-1998 Mazda MPV, it is specified as an upstream oxygen sensor. If your Mazda 6 or Mazda MPV has a fault code related to oxygen sensor performance, this part number provides the correct application-specific replacement path.

Because oxygen sensors influence fuel control and catalyst monitoring, a failing unit can contribute to rough running, higher fuel use, increased emissions, or a malfunction indicator light. Walker Products 350-34140 is manufactured for the intended fitment position so the ECU receives the expected diagnostic feedback.

What It Helps Address

• Check engine light related to oxygen sensor performance
• Rich or lean fuel mixture concerns
• Reduced fuel economy from inaccurate exhaust feedback
• Elevated exhaust emissions
• Poor engine operation tied to sensor signal issues

Installation Notes and Tips

Verify the vehicle’s exact year, engine/emissions configuration, and sensor position before installation. Confirm the connector shape, wire count, thread diameter, and harness length match the original sensor. Inspect the sensor wiring harness and connector for heat damage, abrasion, or corrosion, since physical damage can shorten service life and affect signal quality.

For Mazda 6 downstream applications, confirm the B1S2 or California-ESV bank 1 sensor 2 location before replacement. For Mazda MPV applications, install in the upstream position specified for the vehicle.

Quality Assurance

Walker Products has produced engine management and oxygen sensor components since 1946 and operates under Automotive ISO9001/TS 16949 certification. The 350-34140 is part of the Walker Products Aftermarket line, which is focused on application-specific replacement parts for modern vehicle diagnostic systems.