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DIY How to replace Oxygen O2 Sensor Mercedes-Benz

Step by step instructions on how to change the Oxygen O2 Sensor in your car.

Is you check engine light on because of a bad oxygen sensor? You don’t have to spend your life savings to replace a defective O2 sensor. Here we will show you the steps you need to follow to replace an oxygen sensor successfully.

To replace the oxygen sensor (O2) you will need:

New Oxygen 2 Sensor, which you can purchase online and save a lot. If you go to Amazon, you will see that new oxygen sensors prices for Mercedes-Benz cars range between $30 to $80.Click here to find the right sensor for you car on Amazon.

Oxygen Sensor Removal Tool Removing the oxygen sensor from the exhaust pipe can be a challenge. Especially when there is little room between the oxygen sensor and the car frame or the engine. If you are removing the downstream sensor you may be able to get away using a wrench but to remove the upstream sensors you will need oxygen sensor removal tool set.

How to replace the oxygen O2 sensor. Step by step instructions. 

Step 1: Get the fault codes. 

Scan your car’s ECU using an OBD 2 scanner. If you have not used an OBD II scanners before it is very easy. You will need an OBD scanner to get the fault codes. Here are the bestseller OBD 2 scanners on Amazon and any of these will work fine. Your OBD II port where you plug in the scanner is located under the dash, usually right under the steering wheel. You can see an example in the picture below. obd port scanner

Step 2: Locate the defective oxygen sensor. 

Once you scan your car, you will get a fault code that directs you to the faulty oxygen sensor, for instance, Bank 1 Sensor 2. Which sensor would that be? There are usually four oxygen sensors on your Mercedes-Benz. Look at the picture below to locate the sensor that needs to be replaced. The picture is shown with the engine removed, but you don’t need to do that to replace an O2 sensor ;). location of oxygen sensor bank mercedes benz

Step 3: Remove the undercarriage to access the Oxygen Sensor. 

Most modern cars including Mercedes-Benz have a plastic cover that goes under the car. Don’t let that intimidate you. The engine undercarriage plastic (engine splash shield) is usually held in place with several 8 mm plastic bolts or with push pins.  Once you remove the undercarriage cover, you should see the oxygen sensors.

location of oxygen 2 sensor car

Step 4: Unplug the oxygen sensor electrical connector. 

Separate the electrical connects by pulling it apart. In some cases, you may see little tabs that you will need to press to be able to unplug the old oxygen cable connector. unplug the oxygen sensor connector

Step 5: Remove the oxygen sensor wire from the clips. 

The oxygen sensor cable will have one or two clips that hold the O2 sensor wire. Remove the wire from these clips. You pull on the clip and slide out the cable. remove the oxygen II sensor wire

Step 6: Place oxygen sensor removal tool on the old sensor.

Start by placing the oxygen sensor removal toolon the old oxygen sensor as shown in the picture below. How to place the oxygen sensor removal tool on your O2 sensor, demonstrated on removed sensor. oxygen sensor removal tool installed

Step 6: Remove the oxygen sensor. 

Next remove the old oxygen sensor. Once you place the O2 removal tool on the O2 sensor, you will need to turn it counterclockwise to remove it. oxygen sensor removal tool

Step 7: Install new oxygen sensor. 

Install the new oxygen sensor, which we showed you how to buy online for under under $100 in reverse order. It is recommended to apply anti-seize compound on the threads of the new O2 sensor. It will help to prevent seizing of sensor, makes it easier to remove it next time.

Torque Tightening Specifications

You can install the sensor by hand, and once it is hard to turn then, you can go an extra 1/2 turn using your wrench. If you need to be precise you can also use a torque wrench to tighten the sensor to specifications, torque to 55 Nm or 40 ft-lbs.

Frequently Asked Questions

Where to buy cheap oxygen sensor for my Mercedes-Benz?

If you are looking to purchase a replacement oxygen O2 sensor and save a lot on the part cost, you can find the right sensor for you car on Amazon. See this list we put together of O2 sensors that fit Mercedes-Benz cars. You should be able to enter the year make and model of your car to narrow down to the exact fit for you car. You should see a list from less expensive to the Original Equipment (OEM) brands such as Bosch oxygen sensor on the list.

What is the cost to change Mechanic / Dealer? 

You will probably know the answer to this one already. To replace the oxygen sensor can range from a few hundred dollars if you use your independed mechanic and as much as $1000. Replacing the oxygen sensor is a task you can tackle yourself and save a lot of money.

How difficult is it to replace the oxygen sensor? 

The answer to this question depends on which sensor you need to replace. The downstream sensors are easy to access and thus easy to replace. The upstream sensors can be more difficult to reach, which makes it harder to remove. That’s why you will need an oxygen sensor tool to help you with this task.

Applicable Models

These instructions should help you to replace the oxygen sensor in any car. They especially apply to Mercedes-Benz car models such as C E S CLK CLS CL ML GLK GL SLK SL classes.

How to Video

Watch this very informative video on how to replace the oxygen sensor.


Check Engine OBD 2 Fault Codes related to Oxygen Sensor.

Here is a list of some fault codes related to oxygen sensors but there could be more codes not shown in this list.


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