Walker 350-34987 Oxygen Sensor - Downstream

OE-Style Downstream Oxygen Sensor

Walker Products 350-34987 is a specific-fit heated oxygen sensor built for downstream applications on select Toyota, Mazda, and Scion vehicles. It is engineered as an OE replacement sensor to deliver the diagnostic feedback the ECU expects, helping maintain proper engine management and emissions control.

For drivers searching for a downstream oxygen sensor for a 2015-2019 Toyota Yaris, 2016-2018 Mazda CX-3, or 2016-2018 Mazda MX-5 Miata, this Walker Products Aftermarket part number 350-34987 is matched to the listed application and connector style.

Key Features

• Heated oxygen sensor for downstream placement
• Specific-fit design for direct application matching
• 4-wire configuration with female connector
• Threaded mounting type with 18.0 mm thread diameter
• Wiring harness length: 12.59 in.
• Overall length: 15.74 in.
• Radiused polygon connector shape

Product Details

Walker Products Aftermarket focuses on engine management and oxygen/air-fuel sensors engineered as OE-style replacements for a wide range of vehicles. Part number 350-34987 is built for downstream sensor locations and is intended to provide the ECU with the correct feedback for emissions and fuel-control monitoring. The heated design helps the sensor reach operating temperature quickly, which is important for stable readings after startup and during normal driving.

This part cross-references no listed interchange numbers in the supplied data. It is a direct-fit oxygen sensor for the specified Toyota Yaris, Mazda CX-3, Mazda MX-5 Miata, Mazda MX-5, Toyota Yaris iA, and Scion iA applications listed below.

What It Helps Address

• Check engine light related to downstream oxygen sensor performance
• Poor fuel economy caused by inaccurate exhaust feedback
• Elevated exhaust emissions from a failing sensor
• Rough engine operation tied to incorrect ECU input
• Fault codes stored in the ECU for sensor circuit or response issues

Installation Notes

• Verify the vehicle uses the downstream bank 1 sensor 2 position where noted in the fitment data.
• Inspect the sensor wiring harness and connector for heat damage, abrasion, or corrosion before installation.
• Confirm thread diameter, connector shape, and wire count match the original sensor.
• Check for exhaust leaks or related engine management faults that could affect sensor readings.

Quality Assurance

Walker Products has manufactured engine management components since 1946 and operates as an Automotive ISO9001/TS 16949 certified company. The brand’s oxygen sensor line is developed for application-specific fitment and ECU feedback requirements on modern vehicles.

Vehicle Fitment

• Fits 2019 Toyota Yaris, downstream.
• Fits 2015-2017 Toyota Yaris, downstream.
• Fits 2017-2018 Toyota Yaris iA, downstream.
• Fits 2016 Scion iA, downstream.
• Fits 2016-2018 Mazda CX-3, downstream.
• Fits 2018 Mazda MX-5, downstream.
• Fits 2016-2017 Mazda MX-5, downstream.
• Fits 2016-2018 Mazda MX-5 Miata, downstream.