Check engine light is indicating I need a new "back" or "rear" O2 sensor. I am unable to determine what part # this refers to. Also am unclear as to the location of the sensor. Have determined from other posts that if I lift the passenger carpet I can find what I believe to be the connection for the electric, but I am uncertain as to which sensor this goes to.

Any help, guidance, etc would be appreciated. My skills run to the brakes, belts, alternator level, but this would be first DIY repair on the MB. I am just reluctant to give away 250$ on what I gather from other threads to be a "5 minute repair"

Also, does the Mustang 302 O2 Sensor trick apply to this repair?

How is the CE lamp telling you that a back O2 sensor is needed??

I also went through the odyssey of the CE light indicating an 02 sensor needed replacement. Unfortunately, once replaced (by my shop) the light continued to come on. Despite resetting, the light would come back on every 200-300 miles indicating various causes. My mechanic told me to be patient until it displayed a consistent error.

Ultimately (long after both O2 sensors had been replaced) the light just quit coming on. Whether the car healed itself or the light burnt out I do not know.

Good luck in chasing down the problem.

__________________
David

2010 E350 Coupe / 1K miles
2007 ML350 / 18k miles (Gone, gone, gone!)
1995 E320 Wagon / 170k miles
2008 Audi A6 4.2 / 12k miles
2006 Mitsubishi Endeavor / 25k miles

CE Lamp didn't indicate the problem, my dealer did. It has gone off twice and read the same, indicating the problem is in the back O2 sensor.

I see..
Well, , to my knowledge, your car does not have a rear sensor.
You may just want to open the hood and get the codes from the Push Button sw next to the battery.. that will be a good start for diagnosis...
The code retrieve info can be found in the archives.