Replacing downstream O2 sensor bank one passenger side

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2007-2014 Mercedes-Benz C-Class (W204)

2007年から2014年にかけて製造されたMercedes-Benz C-Class (W204)は、「極めて頑丈」なビルドクオリティと、先代モデルよりシャープで角張ったデザインを優先した、ブランドの復権を象徴するモデルです。

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Ali E. @alie91204

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投稿日: 2026年9月28日

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Replacing downstream O2 sensor bank one passenger side

Hello everyone, I'm trying to replace the downstream oxygen sensor on my 2014 c300. I took it to my mechanic. We removed the plastics and we realized that the O2 sensor is placed inconveniently on top of the Cadillac converter which is very unaccessible. My question is that do we need to remove the exhaust like completely and how do we disconnect the sensor wires because they're placed behind the engine and there is no access neither from bottom nor the top. I feel like even if you do attempt to remove the exhaust we still wouldn't be able to reach the cable from the bottom. I watched a few videos on YouTube and most of them are removing the left side sensor or the ones that are removing the right side. The sensor is located conveniently at the bottom of the Cadillac converter which makes a lot more sense.

Any help is appreciated

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Malcolm Parker @malcolmpar95155 評価: 507 3 · Answer 1 · 2026-09-28T13:28:55-07:00

On those W204s, the sensor itself is usually the easy part. The connector is the pain in the ass because it’s up around the rear of the transmission/bellhousing area. On the M272 C300, Bank 1 is the passenger side and Sensor 2 is the downstream sensor after the catalytic converter.

I’d try reaching the connector from underneath first with the car safely supported. Depending on how tight yours is, you may need to loosen/drop the exhaust a little for access.

Before tearing the exhaust apart, trace the sensor wire all the way to the connector and see exactly what’s holding you up. If the wiring and connector look good, then use a 22mm/7⁄8" O2 socket or wrench on the sensor. Don’t pull on the sensor wire to try to get it loose.

Also, if you’re replacing it because of a code, check the wiring and connector before buying the sensor. Those connectors can get contaminated or damaged and give you the same symptoms as a bad O2 sensor

2007-2014 Mercedes-Benz C-Class (W204)

Replacing downstream O2 sensor bank one passenger side

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