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Hello everybody! My name is Tyler from Mesa, AZ. I just financed a 2012 C250 1.8L Turbo (Blue Efficiency), with 74,000 miles. I've always loved Mercedes but this is my first one. The regular market price for my car is around $12,000. We got a smoking deal at $8,000. The dealer said that he discovered that is has a bad MAP sensor and that he was too lazy to do the job so he just lowered the price of the car.
So The car had a CEL on when I bought it. Yes you heard that right. I went through with it because he said he guaranteed that it was the MAP sensor that is just bad. So after bring it home I purchase a new MAP sensor (Bosch) from Autozone. The next morning I install the new MAP sensor and I clean the throttle body while I'm at it. I go to turn the car over and it starts but enters limp mode. After a bunch of stress and troubleshooting I decide to put the old MAP sensor back on, now the car is no longer in limp mode.
The car has a rough idle, the dealer was "sure" that it was the MAP sensor... Since it doesn't seem to be the MAP sensor, what else should I check for rough idle?
I love my new (used) car and I am dedicating the next month to all the preventative maintenance I can possible perform to keep it running as long as possible. Glad to be here!
(These are the only pics I have so far. Once I get around to fully detailing the car inside and out, I will post more.) ht tps://imgur.com/kPm4qIi https://imgur.com/kPm4qIi
The previous owner is full of shaite. You don’t lower a car’s price by $4000 for a $100-$150 part. Figure it out in the next week. The longer you wait, the higher the chances he tells you it’s your problem.
Since it doesn't seem to be the MAP sensor, what else should I check for rough idle?
These can be great cars when everything is working right. They can have some frustrating problems when something is not.
It could be the MAF sensor, however, parts swapping gets expensive.
And it may be some other components and not one of the sensors.
It might still be a good deal, but methodical diagnosis is needed.
There will be a diagnostic code stored with the CEL. You can take it to AutoZone where you bought the MAP sensor that didn’t work and they can read the codes. An independent shop with a scanner can get more detail but will also charge to do it.
Get the codes read at AutoZone and report back. Then people here can give more useful advice.
No work has been done to the car since I last posted. The rough idle has gone away almost completely, although during acceleration it's still a bit jumpy.
I took it to this repair shop, Star Service in Tempe, AZ, and they ran the code scanner and the car is displaying 4 different codes right now:
(I am just copying directly off the paper that the mechanic wrote all the codes down on)
1. P023400 - Boost pressure too high
2. P17222 - Mixture bank 1 too rich
3. P0606 - Comp Y3/8n4 Transmission Control Unit fault
4. P0705 - Selection Range Sensor A has elec. fault
After handing me the paper with the codes written on it, the mechanic said that "the car is too new" for them to be able to work on it. I called another guy who was referred to me by my sister, Hector, and he says "of course 2012 isn't too new for me to work on, bring it by on Monday."
I also called Mercedes and they said it would be a $350 diagnostic fee, which would be subtracted from the cost of the repair should I choose to proceed.
Is there any other information I could provide that would be helpful? Could it be the same issue causing multiple CEL's?
Shop number 2 will need to check if the codes are stored, active, or pending. They may decide to clear the codes and see which ones come back. At least one of those codes became active to turn on the CEL.
P0234 could be caused by a sticky waste gate and not a difficult repair.
P17222 is the one that relates to a possible bas MAF/MAP sensor. But it could be from leaky injectors or even bad oxygen sensors.
P0606 is a failed transmission control unit or bad transmission electrical connection.
P0705 is a problem with the transmission range selector. It also can relate to a bad electrical connection, so a bad wiring harness could be a common cause with P0606.
The transmission faults are unlikely to be related to the engine faults.
The used car dealer probably pulled the codes and told the sales staff they would give an extra $250 to whoever got it off the lot. And you were told a partial truth about the simplest possible fix. If the car drives OK, it might not be too sick. It’s a bit unusual for the transmission codes to show up without noticeable drivability issues. However, if you don’t drive the car hard, a sticky waste gate may not be noticeable. Leaky injectors could just waste fuel and fail emissions testing.
Funny enough, the car lived it's whole life in Houston, Texas (I saw your location on your bio). I just did the math and the car has had an average of 6,400 miles per year put on it. Yes I will definitely update this thread after this second guy takes a look at it.
Let's say worst case scenario for the TCU is that it has to be replaced. Do I have to go through Mercedes and buy brand new? They are charging $500 for the conductor plate and $1300 for the valve body. How does Mercedes work with replacement parts, they must be programmed in, right?
Thanks for all the help, I've been learning everything I can about how a Mercedes engine operates and it's fascinating. I'm going to keep the driving to a minimum until I get this tranny issue figured out.
6400 miles/yr is very low for the Houston area. My C250, which is the 2nd car, gets 11,000/yr. The primary people hauler gets 23-24,000/yr.
TCU (which is on the conductor plate), and valve body do not have to be bought new. It’s unlikely the valve body is bad at that mileage. But whatever parts are used, the shop must be familiar with the drive authorization system (DAS) to sync all the parts. The DAS is basically the anti theft system. It integrates the ignition switch (EIS), steering lock (ESL), transmission, and ECU. Unless it’s happy, you don’t drive anywhere.
You should have DAS4. If you want to plunge head first into Mercedes details, this is a description of DAS4, courtesy of a member from the E Class forum. Don’t drive yourself crazy, this is high level tech stuff.
I work in tech, I love it. I want to learn exactly how this car works haha. So thanks for providing some documents. I've been doing a lot of research on the DAS, but I can't seem to find out if I'm able to purchase a unit to do the DAS configuration myself, or at the least find some shop local to me that has it. Do you have any documentation/links you could share on the all the software that is used to work on Mercedes? Like, I know there is diagnostic software (Xentry and what not), but I'm not having much luck determining which units can do the programming and DAS config.
Xentry is the “big boy” of Mercedes Benz diagnostics software. Kits are available online. It can do anything that’s needed as long as the version covers the car you’re working on. I don’t have it because I have a mid level Autel scanner. Lots of people in these forums use Xentry. Scanners from iCarSoft, Autel and others are good and many can be configured to do anything that’s needed with the proper add-ons.
For repair instructions, the repair manual known as the WIS can be bought online. eBay is a good source. For under $20 a version that includes the car you’re working on can be had if you’re not interested in the most up to date.
I have a technical background in measurements and networking. I enjoy seeing how things work and fixing them. But for the past two years, my workspace and shop have been occupied with other priorities. I’m limited to routine maintenance until this summer. I have a good friend and a factory trained acquaintance who I can fall back on when I have an issue that I can’t address.
When working on Benzes, you’ll find that some things seem over engineered. There are things going on in the background that you would never know about unless they fail. I think that’s because of their design philosophy of covering every detail 100% and not settling for the the 80% solution. Lots of people show their frustration with this in the threads. Something you will see, though, is that Mercedes sometimes suffers from low volume production. They don’t have a background of millions of cars on the road in many models to quickly flush out failures. A good thing is that over it’s run, there were a few of million W204s built.
So Mercedes just called me back. They have diagnosed the car. Apparently, it needs a new valve body. They are quoting me $2995 for the full job. I've called about 7 other repair shops/transmission shops/etc. and none of them are able to replace the transmission. They are all also telling me that the only place that this repair can be performed is at the Mercedes dealership by certified techs.
Any advice? Besides Mercedes, is there anywhere I can take it to get the job done? If I have to go through Mercedes will they let me finance it?
Is the dealer responsible at all? They told me that they had it inspected and that they "guarantee" that the MAP sensor just needs to be replaced. Obviously, this is not the case. Please let me know your thoughts.
Silver Lining: They gave me a 2022 GLC 300 as a loaner car, and it is sooo unbeveliably nice inside. The steering is so sensitive yet tight. The ride was soo smooth and quiet, it is amazing.
So Mercedes just called me back. They have diagnosed the car. Apparently, it needs a new valve body. They are quoting me $2995 for the full job. I've called about 7 other repair shops/transmission shops/etc. and none of them are able to replace the transmission. They are all also telling me that the only place that this repair can be performed is at the Mercedes dealership by certified techs.
Any advice? Besides Mercedes, is there anywhere I can take it to get the job done? If I have to go through Mercedes will they let me finance it?
Is the dealer responsible at all? They told me that they had it inspected and that they "guarantee" that the MAP sensor just needs to be replaced. Obviously, this is not the case. Please let me know your thoughts.
Silver Lining: They gave me a 2022 GLC 300 as a loaner car, and it is sooo unbeveliably nice inside. The steering is so sensitive yet tight. The ride was soo smooth and quiet, it is amazing.
any local mechanic with experience with german cars should be able to do it...
So Mercedes just called me back. They have diagnosed the car. Apparently, it needs a new valve body. They are quoting me $2995 for the full job. I've called about 7 other repair shops/transmission shops/etc. and none of them are able to replace the transmission. They are all also telling me that the only place that this repair can be performed is at the Mercedes dealership by certified techs.
Any advice? Besides Mercedes, is there anywhere I can take it to get the job done? If I have to go through Mercedes will they let me finance it?
Is the dealer responsible at all? They told me that they had it inspected and that they "guarantee" that the MAP sensor just needs to be replaced. Obviously, this is not the case. Please let me know your thoughts.
Silver Lining: They gave me a 2022 GLC 300 as a loaner car, and it is sooo unbeveliably nice inside. The steering is so sensitive yet tight. The ride was soo smooth and quiet, it is amazing.
I don’t quite understand 7 shops turning down the job. Replacing the valve body, if that’s all, isn’t a particularly difficult job, even on a Mercedes. Are there any German car specialists in your area? Most of them can repair MB along with the other brands. It might be worth searching a 50 mile radius.
A rebuilt valve body is about a $600 part. Then there is replacement fluid, filter, gasket, etc. There’s quite a bit of labor, but you should be able to get a better price than the dealer. I have never seen a dealer that finances repairs, but you can ask.
As far as what kind of liability the selling dealer has, that depends heavily on your state laws. But what they tell you doesn’t hold much weight against what is written in the sales contract. Here in Texas you have 3 days to return a car without question. Beyond that, you have to be able to prove some kind of violation.
Yes. A new GLC is nice, but it’s about 8x what you have invested in the C250.
I finally found a shop reasonably that is capable, but they want $2400 for the job. After deducting the diagnosis fee, that's only $300 less than the dealer. Also, Mercedes of Gilbert approved me for $3000 in repair credit (at an insanely high-interest rate, but it's not looking like I have much of a choice right now).
I only have one more question (for now). Do you guys think it's worth it? It doesn't seem like there is anything else wrong with the car. Would you move forward with the transmission repair, or return it (let's pretend that's an option in this theoretical)?
I just wanted to give an update on my C250. Had it diagnosed at both Mercedes of Scottsdale and Mercedes of Gilbert and they both declared a bad valve body. Gilbert Mercedes charged me $3,000 to replace it. I've had the car back for one day. It seems much smoother and precise. I can feel the transmission shifting between certain gears at certain RPM's that I did not feel before. The shifts feel much smoother and exact. I am very impressed with the transmission work so far.
The car is still sputtering rpms here and there. Not sure what's going on there, so I have to figure that out now. And the pedal still loses power at the apex of a turn (which I'm chalking up to a very awkward feature of Mercedes's electronic throttle body until I can figure out what it is).
I guess $1100 in labor isn't so bad for this kind of job.
They also found some other things in the multi-point inspection: motor and tranny mounts need replaced, front sway bar needs replaced, rear breaks need replaced, and I need to get service A and service B done. Oh and he said I need new tires.
1-A 2012 C250 is Direct Injection (DI) not Multi Point Fuel Injection (MPFI). Maybe the sputtering is related to what the dealer found.
2-Engine mounts are rather expensive at a dealer. The vibrations are usually very objectionable when bad.
3-The sway bar would only need replacing if it was damaged by hitting something. But bushings and links go bad over time, miles, and road conditions.
4-You don’t need A & B service. B includes everything in A. An independent Mercedes shop could save you about ½ the dealer price.
5-You could buy tires at the dealer because the prices through mbusatirecenter.com are competitive and even sometimes lower. There are 50 or more original size tires that fit W204 cars, so a multi brand shop or source may have a wider selection.
6-Losing power at the apex of a turn could be a mismatch between the performance characteristics of the engine and your driving style. Do your RPMs drop below 1500 in the turns? The emgine doesn’t have much torque at all below 1500, and if you’re in E mode, coming out of a turn asking for power just isn’t there. Try S mode which keeps the RPMs up by changing shift points, or bump the tranny down a gear by pulling the lever left as you try to accelerate. There are some tricks a tuning shop can do without any hardware, but try S first.
So the car stalled at a red light today and it is idling very rough. I forgot that there was a CEL for the tranny and another for the engine from the very beginning. They fixed the valve body but now I'm left with this final (for now) issue, P0172 - engine bank 1 too rich.
I am getting it diagnosed at Mercedes again, this time for the engine issue. Hopefully it's something small!
Could it be spark plugs? Maybe I should try replacing them before I get it diagnosed again.
Spark plugs are probably not the cause of that code. But they are fairly inexpensive, and easy to change. I recommend using the MB plugs because they are pre-indexed and that’s important on DI engine.
P0172 sounds like it may be a leaky injector. The O2 sensor is usually where the measurement is made.
I just got the car back from Mercedes. They are saying that it's either a bad throttle valve (throttle body?) or a bad ECU, and that they have to rule out the throttle body first because the ECU can't be returned after it's installed and the throttle body can. I'm losing my will to continue this fight. I just bought the car, already done a $3k valve body replace, and now they want $2400 for the throttle "valve" replace and $1100 for the ECU replace, depending on which it is.
I already had to finance half of the valve body repair, I can't afford another $2400. I know a lot of you are probably going to say "well then you can't afford to own the car". Please refrain from that. I already know I made a bad decision. I was just excited to own a Benz and it genuinely did seem like a good deal.
any possibility of taking it to the original dealer you bought it from and disclose all these problems to either get even more discount or refund some of the costs youre taking on?
Wow — the throttle body is a $1500 part new at the dealer. Online prices are ¼ of that for a quality aftermarket part.
Following spb147’s suggestion, you have nothing to lose by going back to the seller. If they refuse, you’re no worse off. There have been so many expensive problems with this car, I wonder if you would get any relief in small claims court claiming “not fit for purpose.”
You may be at the point where you need to invest in pro level diagnostic equipment, take the car out of service, and become a serious DIYer. That would preserve your investment, but if it’s your daily driver, maybe not possible. And that will still cost money and you aren’t very experienced with Mercedes.
Maybe you could see if you can trade it in and get something with a note you can afford. The dealer has already been into it and knows what it will take to get it running right. It’s too old for the CPO program so I don’t know what they would offer you as a trade because they may not want it for their lot. Another brand dealer is going to be very reluctant to trade a car with the CEL on. And you probably aren’t looking to finance for 7 years, either.
Thanks for the replies guys. It really helps to hear outside, unbiased perspectives.
I am picking the car up in a few hours (dropping off the 2022 GLB 300 (2nd) loaner, it's soo nice). I do believe the dealer is somewhat responsible so I am going talk with him and see if we can make a deal. If not, I am going to file a suit in small claims court. He guaranteed us that is was just a MAP sensor, so it's technically false advertising, or IDK what you would call it but something like that.
As for the car, I'm going to keep it because I'm already invested into it even more so than just the monthly car payments. I think once I get this issue ironed out I will be good.
@Odd Piggy I would love to become a serious DIY'er. What would I have to buy to be able to do things like program ECU's to the computer, you know, the DAS pairing and what not? And does a throttle body have to be programmed after it's installed? Or is it just the ECU that has to be programmed?
I've been an audio engineer for 16 years and a computer network engineer for 3. I love learning how things work, so serious-DIY is definitely something I want to do.
@Odd Piggy I would love to become a serious DIY'er. What would I have to buy to be able to do things like program ECU's to the computer, you know, the DAS pairing and what not? And does a throttle body have to be programmed after it's installed? Or is it just the ECU that has to be programmed?
I've been an audio engineer for 16 years and a computer network engineer for 3. I love learning how things work, so serious-DIY is definitely something I want to do.
Awesome, thanks. So this place by my house iAutohaus, will do the throttle body replacement and retraining ("if needed") for $1000. That's $500 less than the part alone at MB. lmao how ridiculous. If there is still an issue then I'll have to get the ECU replaced at MB (ugh). Surprisingly they are only charging $1100 for the job. The mechanic at iAutohaus says he almost never sees an ECU that needs replaced, so... we'll see.
I will probably have iAutohaus do the throttle body so I can be up and driving. But very interested in being able to fix this car myself (and just understand how it works in general). I'll barely be putting any miles at all on this thing, so hopefully maybe I can even sell it for more than I paid for it one day. lol.
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