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Location of the Automotive Oxygen Sensor?

2 Answers

OLillian

07/29/25 4:44pm

An automobile has two oxygen sensors, installed in the exhaust pipe. Below is an introduction to the two oxygen sensors in a car: 1. One is located before the three-way catalytic converter, referred to as the primary oxygen sensor or upstream oxygen sensor, used for mixture feedback control. The engine control unit adjusts the fuel injection quantity based on the feedback signal from the primary oxygen sensor, maintaining the actual air-fuel ratio close to the theoretical air-fuel ratio, to detect the oxygen concentration before catalytic conversion. 2. The other is located after the three-way catalytic converter, known as the secondary oxygen sensor or downstream oxygen sensor, used to monitor the catalytic purification efficiency of the three-way catalytic converter. When the three-way catalytic converter is damaged and its conversion efficiency is lost, it is almost equivalent to not having a three-way catalytic converter installed. The signal voltage waveforms of the front and rear oxygen sensors become similar, and the voltage fluctuation ranges also tend to be consistent, indicating a decline in the conversion capability of the three-way catalytic converter.

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DiAnthony

08/14/25 6:18am

I usually enjoy DIY car repairs. The oxygen sensor is located in the vehicle's exhaust system, typically in two places: one is the upstream sensor, positioned near the exhaust manifold or engine outlet, close to the engine; the other is the downstream sensor, installed directly behind the catalytic converter. When checking, I always have to be careful because the exhaust pipe gets very hot to avoid burns. If the sensor is misaligned or loose, the car will trigger a warning light, fuel consumption will spike, and black smoke may appear, affecting overall performance. Once, my old Honda had excessive carbon buildup on the sensor, causing engine stuttering—a simple cleaning fixed the issue. Different car models may have slightly different sensor placements; some newer models might have multiple sensors located under the chassis, making them harder to see. I recommend using an OBD diagnostic tool to help locate them—it's efficient and accurate. Regular cleaning can extend the sensor's lifespan.

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