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Hello. We have a check engine light with the OBD2 code giving us a P0018 code on a 2012 E350 Coupe. The car idles and runs fine, however, there is a noticeable delay at key ignition start.

The next step for us is to pull the left intake cam sensor and turn the crank to the “305” position and verify that the mark inside the sensor hole is centered. If all aligns well, is it safe to assume we just have a faulty camshaft position sensor? Could we swap sensors to see if the issue moves to another position?

We are in California, and with the check engine light, we are under the gun to get it corrected because smog is due in the coming months.


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It's pretty standard to swap the sensors to see if the problem moves with the sensor or not. Not sure how much those puppies cost but that would be a factor in my decision to move vs just replace it.
I'm sure your alignment is correct because if the chain jumped a tooth it would run worse. So if it were me I'd going with sensor. I always buy from somewhere other than the dealer if possible, just be sure it's a quality part. Like many parts are Bosch or VDO etc, which is should say on it, then I just buy that part for rockauto, fcp euro etc. Up to you tho... Good luck!
 

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Thanks, chevota.

The engine is said to be an M276.
Is it true that the cam sensors are accessible via removal of the intake manifold? Is this difficult? Will this involve replacement of other parts, like seals?

I also cannot find much info on the process to access these sensors on the left “hard side.” Anyone with pics, manual pages, or links to videos? It’d be much appreciated.


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Assuming you have the same eng I did, with the big funky flat intake on top, then I believe the sensors are well hidden under it. If you have the ECU computer on top center then the intake is a non-issue. With mine, had I ever needed to remove the intake, I discovered the gaskets were expensive and at the time out of stock, apparently world wide. Even if in stock I wasn't going to pay for them so I would've just put a bit of silicone on them, if needed. Anyway, couple vids of the two engines:
youtube.com/watch?v=1jcf-TAXW0Q
youtube.com/watch?v=Xpeq2UWDmuk
The latter being my engine, intake removal, and the hidden sensor at the 3:03 mark.
If you have the same eng as I did, then swapping the sensors and running the car is not so easy, so I'd just buy all new sensors which I think are like $25ea for the good stuff?
 

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Assuming you have the same eng I did, with the big funky flat intake on top, then I believe the sensors are well hidden under it. If you have the ECU computer on top center then the intake is a non-issue. With mine, had I ever needed to remove the intake, I discovered the gaskets were expensive and at the time out of stock, apparently world wide. Even if in stock I wasn't going to pay for them so I would've just put a bit of silicone on them, if needed. Anyway, couple vids of the two engines:
youtube.com/watch?v=1jcf-TAXW0Q
youtube.com/watch?v=Xpeq2UWDmuk
The latter being my engine, intake removal, and the hidden sensor at the 3:03 mark.
If you have the same eng as I did, then swapping the sensors and running the car is not so easy, so I'd just buy all new sensors which I think are like $25ea for the good stuff?
chevota, thanks for your valuable input.
Here’s what the engine looks like, and I can confirm that it’s an M276 engine:


As mentioned, the check engine light is illuminated and the OBD2 code spits out P0018, which refers to the left cam sensor; said to be the more difficult side to replace, is it not?

In either case, the current owner says that there’s nothing noticeable with the engine while driving the car around. However, there’s a noticeable hesitation upon key ignition start.

Are the chances good that this check engine and P0018 issue is with the one cam position sensor? I would still take heed in replacing all of the sensors ($50 each x4) while I’m in there. FCP Euro has a set of the plenum gaskets and a spark plug set for $80 (all Bosch), so might be worth it.


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Could be the delay is it's looking for the sensor, gives up and starts anyway because it's not that important. Could be something else causing it too. Super hard imo to figure out problems in modern cars. Sometimes the codes make it easier, but I see it like this; the car is 1000 times more complicated than a simple old car with no electronics. The OBD2/EOBD system makes it 10 times easier to find what's wrong, which makes only 100 times harder figure out the issue. Come to think of it, I can't recall one single code that actually lead me to the problem. I can also say I've many problems with no code, and a code with no problem, which by default is impossible to fix.

Note many things are just a bad connection so if you can get to the plug I'd take it off and put it back and see what happens. And inspect the wires and connectors because sometimes they break, or get chewed on by rats.
If the intake has to come off then I'd rather lift it just enough to get the part swapped. Unless you want to change those gaskets. I would rather not so I'd see if works without doing that.
Plugs are also up to you but here's how I see it: Do I care as long as the plugs are still firing? After all it is their only job and as long as they do it why care? If the engine isn't sucking oil from the pcv system they'll last a really long in that car. The major problem I see is oil gets past the pcv system and works on fouling them, and worse is what it do to the intake valves.
A clue is looking for oil at the throttle blade. Mine was dripping wet with oil and a peek into the intake showed much more oil. So that's why I was looking at gaskets, I wanted to clean my valves and the gaskets were just in case I needed them, which I don't believe I would, but the price and availability killed the thought.
Oil tells me the pcv oil separator is bad, or more likely imo they never worked for damn in the first place because oil separation is not easy. So if the intakes are nasty then I'd seriously consider cleaning them. Someone makes a spray foam that apparently works great, then you vacuum out the mess.

If you do change the plugs I'd be extra careful not to break the coils. I'd then look to see if the boot was sealing dirt out or not, if not I'd blast out the hole with shop air before I pulled the plug so crap doesn't fall in. I think it may take a special socket to pull the plugs, like my M278 does. At least in my case the hole is so small a regular socket won't fit, and that eng is more or less the same as mine so I assume the holes are the same. So look into that...
They say never to put anti-seize on plug threads, but screw that! Those heads are aluminum and I've had too many friends go to pull out plugs and it trashes the threads. Some cars it's common to see replacement steel inserts in the head for the same reason. The story is the anti-seize will hinder heat transfer causing the plug to run hotter, but I don't believe it possible, nor have I ever see any evidence of it. Even if it did, who cares, and if someone were obsessed over it then simply buy a colder plug. No matter what it's much better than stripping the threads. I suggest copper base antiseize but I make my own from tungsten disulfide, or the copper stuff and I add tungsten to it. Note that lube alters the torque value you use, so if you use the same torque # you just over torqued them. Usually not a big deal, but some cars, usually much older ones, this was important because there wasn't many threads so over torque actually stressed them. Your plugs should have a gasket, which I won't go into detail on that as well, but you don't want to crush it more than needed with too much torque. I do it by feel, but if using a tq wrench I guess shave off 25% with lube?
Pulling the socket off after the new plug is in can be a pita too, which is why the official MB socket has a non-removable extension. Otherwise you may have to remove the plug to get your socket back, then have to figure out how to do it again minus pulling the plug. Lube is usually all it needs, but often I have to modifying the rubber inside the socket so it can't hold the plug so well. Same with the plug boot/coil, it may not want to come off easy and those coils are expensive so be careful. Then when you put it back be sure and put silicone grease inside the boot with a Q-tip or something so you don't miss a spot. Most think it's for the spark, but it's not, it's mainly to make pulling the boot off easier next time but also makes it easier to install the boot which is important since these ones are so expensive.

So if you're super lucky you could pull it off with no parts and barely any labor, or just one sensor, or you end up doing all that stuff. Most people don't think like I do and would want all the sensors replaced, and the plugs. Or, if a business, and you change one sensor and charge xx $, but then the other one goes the next day you'll have an angry customer that wants you to fix it at no additional charge because they think you did it wrong. So if you replace all the sensors it's not your fault.
Or you can get a quote from the dealer to do all this, then decide to buy all the parts, plus buy a new set of tires and still have spent less than half of the dealer quote.

And wash that poor engine! I'm guessing a new air filter too ay?

Couple more I had saved under spark plugs:
youtube.com/watch?v=WslrNB77fWY
youtube.com/watch?v=J9we_nFdj1E
youtube.com/watch?v=HpD3Aq1rYIo
The last being my fav because it looks like he's going to work, but instead decides he must change those plugs right now! Then takes off his jacket and shoes, puts on gloves, yet keeps the white dress shirt on! Only guy ever to wear such an outfit for this job. Either asians are crazy or they have a great sense of humor.
 

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Discussion Starter #7 (Edited)
I’ve seen the last video! That guy is great. Such a stickler for details too. Kind of a testament to being a caring Benz owner and mechanic, in my opinion.

Wow, thank you so much for the great detail and info.

It didn’t take too long, but we ended up gifting the car to some friends who were excited to take on the potential nightmare ahead. Hopefully, they discover that it is an easy matter to lift the intake manifold to get access to the left bank cam sensor. Those plugs are pretty well sealed with the rubber grommets, but I’ve heard that the spring on the metal contacts inside the housing can lose their compression, so maybe just some picking them out to create a better connection to their respective pins might solve the issue?
It all became such a hair-brained ordeal that we decided to release the car and make it somebody else’s problem. I’d hate to be the service manager at any Benz dealership to have to break it to all of these customers at the expense of issues like this. But then again, it’s likely that most Benz owners can afford such repairs. I wish I were more a fan of cars in general. I do appreciate the careful consideration for comfort and all of the engineering that Benz puts into their autos. Still, just as you described, the result of one darn sensor can potentially ruin the entire car ownership experience.

What car should we look at next?

Thank you for all of your insight and links into this, chevota. Take care.


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I had a CLK320 with a P0400 error yet nothing was actually wrong. Can't smog it so I drove it for another few years anyway and got rid of it. What baffled me was there is no sensor for the EGR, the computer apparently takes other data elsewhere and makes the assumption. Problem is everything checked out. So yeah, sometimes it's best to just get rid of a car. I think yours was likely very fixable but it's up the owner if they want to do it. I've learned from experience that even complicated things are generally not that bad if you just dive in and pay attention. Like the first time I rebuilt an automatic tranny, for which there were no instructions and nobody I knew would dare tackle such a job. And it looks pretty intimidating once you're in there but it's really not that bad. I like mechanical stuff and understand it really well so I really I'm saying it was easy for me, but I know many or most are on the other end of the spectrum and they'll never even try because they know better. I still believe most people could do it, but they would need detailed instructions. I've written many instructions for various things and despite my best efforts and explaining every detail I always fall short with someone. Most all instructions are far worse than I write, which I'm sure you're aware. Telling someone how to drive a car would likely start with; turn the key to start the car. If the person has never seen or been in one, then they're standing outside the locked car, can't get in, so with the key in hand they turn the key over. I thought that yesterday when using an instruction of how to remote into a computer a work, which I had never done before and there's all these bs security hurdles too. The very first picture in the instruction is not what I have on my screen so I cannot click on what I do not have. I never used the program before so I was like the car example. I eventually figured it out but it took a couple hours and discovered about half the instructions were wrong.
I'm rambling but I can tell you youtube is a godsend for working on cars. They still almost always leave out important stuff, which is why I added all that info before, but when I was a kid there was no internet and if the local autoparts store didn't have a Chiltons for your specific car, you were on your own or pay the big bucks to have it done. So far the only work I've paid for is tire changes, alignments (but usually do both those myself), and certain machine work like boring cylinders and turning a crank which I simply cannot do without the super expensive tools.
I only took one car to a dealer one time, which was an ML320. It would start fine when cold but if you put it gear it would die. Giving it gas or revving before putting in gear didn't help, you simply had to let it warm up first. Of course no codes and there are no details about how each part or the ECU works, but I was confident there was nothing I could fix so I took it in. Later they called me and said it was the MAF and it would be xx hundreds of $. The MAF is a generic dealer response to everything, and I had already swapped that out. They insisted that was it so I took my MAF, and with the service manager watching, I swapped it out and showed it didn't matter. So they tinkered some more and eventually called to say they couldn't figure it out. So no charge, surprisingly, but I managed to keep my record of never paying anyone do what I could've done. Oh, and the fix was to put a clothes dryer vent hose on the cold air intake so it would instead pull air from over the exhaust manifold. Redneck but it worked. I figured that out when I pulled the air filter out and filled the air box with ice to see if was a cold engine or just cold air it didn't like, it was the cold air... I can only assume the ECU isn't getting the cold air data or it's broke or corrupt and doesn't know what to do with it.

I can't suggest a car, only that I swapped my E350 for an E550 because I wanted the power. For me it also has to be a 2 door so that narrows it way down for me (imo, if it isn't a taxi, a car has no business being a 4 door). Plus it's gotta be cool looking which weeds out all 4 doors, but also weird looking cars like SLK's. I want white outside and 100% black inside which narrows it waaaay down. Then the power I wanted takes it that much further, which is why I had the 350 because I couldn't find a 550. And price of course. I looked at AMGs too but the mileage sucks and unless you get a newer one it's not really any faster, but they do have advantages I want but they also cost a lot more. So my 550 was one of two cars in the whole US that fit what I wanted, one was 100 miles away, the other was 3k away, so narrowed down to one car, which I bought. But yet again I have a mystery issue, which is it runs fine but when you floor it it's missing a ton of power so it's basically no faster than the 350... It was at first, big time faster, but then it wasn't. No codes except some CAN bus codes complaining about, yet again, things that work just fine. So now I have learn about CAN bus to figure out if something may be somehow causing the engine to do what it's doing. Like maybe there's noise in the system so it thinks the engine is pinging, I just don't know... I'd be willing to bet $ the dealer won't know what it is either.
Fyi I think I'm sexually attractive to Gremlins because they follow me everywhere!!!! Specifically electronic issues which is super frustrating because I'm so much better with things I can see, but chips you need prints for and you usually can't find, and tracing an overly complicated board is the opposite of fun. And while I have done that kind of stuff, I find most all electronics are easier to just replace or make a replacement from scratch.
So I guess I'd just buy the car you like the looks of and cross your fingers. Or pay the really big bucks and buy new with warranty, then trade in when the warranty expires. Like my 550 had 28k on it and about $40k off the orig cost. So some rich guy/gal/company leased it and dropped 40k off the price for a mere 28k miles. So would I rather pay the 40k or have a few issues that may cost a few hundred, or even thousand? Worst case I sell it and get another. So let someone rich pay for most of it and take over their scraps. It's really amazing how many people have the $ to spend that much every few years, which is why there are so many low mileage cars available.
Btw, white because it doesn't show dirt as much and water spots are basically invisible, and since I kinda live in the desert it's much cooler. So much so that cars like my CLK, which was a metallic maroon/red, would get so hot in the short time I'd go shopping, that I'd leave it running with the AC full blast while I shopped. Like stuff you leave in the car gets ruined kinda hot. And I had to leave one rear seat down so stuff in the trunk survives. I like metallic silver too but white more. Black inside because it's super cool looking (imo). Some people buy a light cream color interior, which activates my gag reflex. So there's my thoughts ;)
 

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Yes, I’m no fan of the lighter shade interior either. Keep steady with the gremlins and they’ll show you respect in the end.


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