How to Replace Oxygen Sensor for Mercedes Benz C350

The oxygen sensors (also called O2 sensors) are one of the most important elements of the modern fuel injection system.If you find your oxygen sensor was broken,you need to replace new oxygen sensor.So here I want to share the steps to replace oxygen sensor for Mercedes Benz.

 

Time: 2 hours

Tab: $95 to $800

Talent: 3

Tools: 22mm wrench, 22mm crow’s-foot wrench, jack stands, floor jack,wheel chocks, safety glasses, torque wrench

 

Applies to: C350 (2007-14), SLK350 (2004-14), CLS350 (2004-14), CLK350 (2005-14), E350 (2005-14), S350 (2005-14), SL350 (2005-14), R350 (2006-14), ML350 (2006-14), Viano (2005-14), Sprinter (2006-14), CLC350 (2008-14), GLK350 (2008-12)

 

Procedures:

You need to remove the front (red arrow) and rear (yellow arrow) engine covers along with the air ducts (green arrows).Please see article: How to Remove Benz C Class W204 Engine Cover

There are four O2 sensors on the C350:two pre-catalytic convertors (yellow arrows) and two at the rear of the cats (red arrows).The wiring connection are located on the lower sides of the bell housing (green arrows).

This photo shows the two sensors on the left side,the pre-cat (red arrow) and the cat sensor (yellow arrow).There sensors are NOT interchangeable.The right side is the same as the left though.

Both sensors connect to the wiring harness on the lower side of the bell housing.The connection for the pre-cat sensor (red arrow) is different from the cat sensor (yellow arrow) so you can’t mix them up.

Simply pull the connection for the sensor you are changing out from the retaining clip and separate the connection.

While the size of the sensor is 22mm you really should get and use a 22mm Crawfoot socket.The sensors are difficult to reach and can get quite stuck.You Don’t want to round off the sensor trying to remove it.I hightly recommend using the Crawfoot socket.

The sensors can be difficult to get to so have a series of extensions and universals ready.Use the Crawfoot socket and remove the old sensor.

There is absolutely no way to tell if a sensor has gone bad by looking at it,so make sure you have checked the fault codes.The sensors have different length cables with different connections so while they will screw into both ports. You really,really have to try hard install and connect them incorrectly.The new sensor will have small amount of anti-seize on the threads.Make sure you don’t get this on the sensor itself when installing.Installation is the reverse of removal.

Done!