I recently purchased a used (not CPO) 2012 S350 Bluetec with 35K miles. This is my third Mercedes diesel and honestly I have never had this many issues...I'm hoping someone here has seen this set of conditions before. It's still under warranty but dealership seems to be grasping at straws at this point.

First time the CEL came on the OBD code was p2202 (NOx Sensor Circuit Low Bank 1). Took it to the dealership and they replaced both the front and rear NOx sensors, car battery, updated COMAND firmware and reset CEL.

Two weeks later on a long road trip CEL is back on with code P062F (Engine Control Module Internal Circuit Malfunction). Dealership diagnoses bad ECU and replaces it.

One week later CEL is back on with code P062F again. Dealership says connected to STAR ECU is reporting an "undefined" code. States they will contact Regional Service Advisor (RSA). The RSA escalates them to engineering group in Germany. Two weeks go by and engineers respond with "The only condition that could cause an undefined code to be reported is customer flashing aftermarket firmware to ECU". I tell Service Advisor this is crazy, I would never do that. He says he will pass that on to the shop Foreman. He tells me this is the third vehicle in a month that is reporting an undefined code in STAR. He then tells me, according to the service history for this vehicle, the ECU has been replaced two other times at other dealerships! My blood pressure shot through the roof! Why would they keep replacing the ECU instead of tracking down the cause? My research suggests that ECU failure, especially in the S Class, is EXTREMELY rare.

Anybody have any ideas of what to check next? Wiring harness? Alternator? Car runs great (a little rougher at idle than my '08 E320 Bluetec but still 32 MPG on the highway in a car that weighs almost two tons).

 

It's a lemon. Three repairs for the same issue qualifies the car as defective under the Federal Magnuson Moss Warranty act. Because it's still under the factory warranty (4/48k right?) it doesn't matter that you're not the original owner. Mag Moss requires the manufacturer to pay your legal fees as well, so most "lemon lawyers" will take your case for free and charge you nothing if they lose. If they win (and if they take your case they normally will win) they'll bill MB.

Let MB buy the car back and go get another one. Type "<YOUR STATE>lemon lawyer" in Google. They'll usually have a form so you can submit info for a free case evaluation. Some states are better than others. Hopefully you're in a good one.

 

Thanks man. I didn't even consider that. It's still under the factory warranty. I am so frustrated over the situation I'm not really thinking clearly. I told the SA that every S Class should come with a C Class because I have been driving a C Class (loaner) more than my S350 since I bought it.

I'm in California and there are a crapload of lawyers here...if anyone can reccomend a trustworthy one in the Sacramento area that would be helpful.

 

Double post.

 

Years ago I designed and maintained a national lemon law website for a group of attorneys. Back then the heavy hitter was Adam Krohn, who is an enormous douchebag to work for but a very effective attorney. He does practice in CA or at least his firm associates with a CA lemon law firm. I believe CA is fairly "friendly" to plaintiffs.

http://www.krohnandmoss.com/

Complete the free case eval online and that'll get you started. Never any obligation until you actually sign a contingency agreement. Good luck and keep us updated.

I'd avoid telling MB at this point you're considering litigation. Stuff will go south as far as their attitude towards you.

 

Thanks again! I will take your advice and keep my mouth shut when talking to the dealer. My SA already started acting weird when he figured out the ECU had been replaced at other dealerships before they did it themselves. He also did not sound comfortable asking me if I had flashed the ECU and the normal, super positive tone to his voice is now completely gone.

 

It's all about playing nice while quietly gathering all the service records you can get your hands on. Either three unsuccessful repairs on a single issue or a total of 30 days in the shop for any combination of issues triggers the law.

 

Not that anyone is following this thread but I hate when I do a search and someone posts one time (and one time only) about exactly the same problem I am having and then disappears off the internet with no follow up...

Just got a call from my SA and he says that the Foreman sent the whole issue back to the engineering team and they responded today by instructing the dealer to replace the "CDI Module" (no clue what that is) and so they ordered it.

He tells me hopefully things will be wrapped up by next week. I won't go into detail but I am keeping all my options open in case this does not turn out to be the last of this issue. I can't tell you how sick I feel when that CEL turns on.

So, I'm keeping my fingers crossed I won't see it again but at the same time I'm keeping my expectations low. Also kinda getting tired of driving a C250 too...Every day in one reminds me of why I bought an S class...No offense meant to C Class owners but the loaners at my dealership are stripped down and frankly you're lucky to have turn signals and a seat. My cell phone is bigger than the center screen and at least my phone has navigation...