Keep your exhaust readings accurate and your catalytic converter monitored with the Walker Products Oxygen Sensor 350-34957. This downstream (post-catalytic-converter) sensor is a direct-fit replacement for the listed applications, including the 2016-2020 Audi A3, 2019-2024 Audi Q3, 2013-2020 Seat Leon, 2015-2018 Volkswagen Golf, and 2018-2024 Volkswagen Tiguan — see the Buyer's Guide tab for the full list.
Positioned after the catalytic converter, it measures the oxygen content of the exhaust stream and reports that signal to the engine control unit. The ECU compares the upstream and downstream readings to gauge how well the catalytic converter is working and to help keep fuel delivery on target.
Signs this sensor may need replacing include an illuminated check engine light with oxygen-sensor or catalyst-efficiency codes and reduced fuel economy — diagnose the cause first, since the converter or wiring can trigger the same signs.
Interchange: Manufacturer part number 350-34957.
Is this an upstream or downstream oxygen sensor?
It is a downstream sensor — it installs after the catalytic converter to help the engine control unit monitor converter efficiency.
What does a downstream oxygen sensor do?
It measures the oxygen content of the exhaust after the catalytic converter and sends that signal to the ECU, which compares it with the upstream reading to gauge catalyst efficiency.
What vehicles does 350-34957 fit?
Applications include the 2016-2020 Audi A3, 2019-2024 Audi Q3, 2013-2020 Seat Leon, 2015-2018 Volkswagen Golf, and 2018-2024 Volkswagen Tiguan; see the Buyer's Guide tab for the full list.
What are signs this sensor may need replacing?
An illuminated check engine light with oxygen-sensor or catalyst-efficiency codes, or reduced fuel economy. Diagnose the cause first, since other components can trigger these symptoms.
Will replacing this clear my check engine light?
If a failed downstream oxygen sensor is the cause, this replaces it. Have the code diagnosed first, as the converter or wiring can produce the same symptoms.
WARNING: These products can expose you to chemicals including lead and phthalates, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.
