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Some pictures of the cam sensors.
Seemingly no cracks but it looks as if the oil ingress is just below the pins.
Originally Posted by OnlyGerman
YES. Inspect now and replace if you have older part numbers. It is usually overlooked, even at the dealers...
thanks! I dont recall people mentioning this problem on the ML/GLE forums if this is also affecting M276 engines. I wonder if my ML350 did have this problem. So is it prudent to have those pig tail on these cars as sacrificial lambs then? Did anyone installed it on +2017 M276/M278? Just lining up the ducks to whatever I will get and be prepared with some elbow grease.
Last edited by shotgun_banjo; Dec 25, 2021 at 05:52 PM.
another thing if you are getting a 2019 model v6/v8 should you still be worried about this?
2019 models are on the 166 platform so are potentially affected by oil in the harness. These late model 166 models have the latest cam position sensor and cam magnet part numbers, and no oil leakage has been reported yet on this site.
2019 models are on the 166 platform so are potentially affected by oil in the harness. These late model 166 models have the latest cam position sensor and cam magnet part numbers, and no oil leakage has been reported yet on this site.
that is good to hear then. It is this one and the cylinder brushing that is getting me worried on the M278s like what you have said on the other thread.
that is good to hear then. It is this one and the cylinder brushing that is getting me worried on the M278s like what you have said on the other thread.
Oil in harness is far less severe than cylinder scuffing.
Oil in harness is completely curable if caught early enough. The only solution for cylinder scuffing is a new (used) engine that will scuff again unless cylinder sleeves are installed.
Oil in harness is far less severe than cylinder scuffing.
Oil in harness is completely curable if caught early enough. The only solution for cylinder scuffing is a new (used) engine that will scuff again unless cylinder sleeves are installed.
I read somewhere that the newer built M278 has cured this problem but not sure if it is true. Have you seen +2017 M278s having such problems?
They switched to something called nanoslide - iron alloy plasma deposition basically. Non rebuildable since iron layer on the cylinder walls is not that thick for oversize machining. However no cylinder scuffing. Basically your engine lasts as regular engine. But overall - don't feel that good under boost (especially aftermarket) since walls still aluminum alloy.
"The NANOSLIDE® production technology is based on arc wire spraying (Germ. LDS), which was developed from the outset for maximum resource and cost efficiency and has clear advantages over all other thermal spraying processes in terms of process stability, mass production capability and resource utilisation. Using LDS, a 0.1 to 0.15 mm thin, microporous anti-friction layer is applied to the previously activated inner wall of the cylinder and made extremely smooth during finishing."
Last edited by arsupisemnet; Dec 28, 2021 at 08:57 PM.
Hello, my 2013 SL63 had a similar issue! The car misfired and when I took it to Mercedes they found oil leaking from the camshaft sensors and made its way into the ECU and multiple injectors.
I only talked on the phone with the service advisor and he will have an estimate for me tomorrow... I think we all know where this is going...
For context, I got this car last year and I’ve been using it as my daily driver (I work from home, but still drove around 10k miles since I got the car). Also, I tend to drive more spirited. I got the car with 47k miles and got some third party warranty from the Mercedes dealer I bought the car from in Texas. I doubt they will help much...
To make things worse, in November I had the car checked and everything was dry. I talked to my service advise about replacing the camshaft sensors, but decided to do it in April together with the B Service. Unfortunately, 3 months and 3k miles later, oil spread everywhere!
There is really no way of telling when these things might happen, so I would recomed everyone get the updated camshaft sensors as soon as possible.
Hello, my 2013 SL63 had a similar issue! The car misfired and when I took it to Mercedes they found oil leaking from the camshaft sensors and made its way into the ECU and multiple injectors.
I only talked on the phone with the service advisor and he will have an estimate for me tomorrow... I think we all know where this is going...
I'm not sure I'd trust a dealer with this one. I talked to a local indy and he told me they are seeing this a lot and he also told me that they have really good results with thoroughly cleaning the harness. I actually heard that from multiple sources. With that information, I bought a can of electrical contact cleaner (some same break cleaner would also work great) and cleaned every single connection. The amount of oil that was in the ECU connector alone was frightening. However, after all the cleaning work (and replacing one fuse 216 that got triggered) the engine is running smoothly again.
Please consider this alternative before ripping the engine out of the car!
Hello, my 2013 SL63 had a similar issue! The car misfired and when I took it to Mercedes they found oil leaking from the camshaft sensors and made its way into the ECU and multiple injectors.
I only talked on the phone with the service advisor and he will have an estimate for me tomorrow... I think we all know where this is going...
For context, I got this car last year and I’ve been using it as my daily driver (I work from home, but still drove around 10k miles since I got the car). Also, I tend to drive more spirited. I got the car with 47k miles and got some third party warranty from the Mercedes dealer I bought the car from in Texas. I doubt they will help much...
To make things worse, in November I had the car checked and everything was dry. I talked to my service advise about replacing the camshaft sensors, but decided to do it in April together with the B Service. Unfortunately, 3 months and 3k miles later, oil spread everywhere!
There is really no way of telling when these things might happen, so I would recomed everyone get the updated camshaft sensors as soon as possible.
Very sorry to hear. It may be worth to replace sensors and try to clean as much as as you can in the harness. Mercedes sucks, this should have been recalled.
Thank you guys very much for the advice. My Mercedes service advisor is always super helpful, but he has to stick with their price structure...
So the cost to start the repair would be over $14k...
I’m including a screenshot of their recomendation.
Even though these was oil on the camshaft sensors, they found clues indicating that the injectors may have leaked some oil into the harnes. They have seem oil inside harnesses, but the camshaft sensors were dry.
I talked to an independent shop specializing in BMW and Mercedes, they seem to have a great reputation and seemed very involved over the phone. The person on the phone also recomended to just replace the camshaft sensor and clean the oil off all the connectors. I’m thinking of replacing the injectors too...
I’m taking my car to them tomorrow.
The car continues to run with absolutely no issues, even under heavy acceleration.
My third party warrant sais they should cover injectors, wire harnesses and ECUs. However, I’ve noticed that if the part doesn’t actually fail, they won’t cover preventive work... Which is anoying since they won’t cover any subsequent damage caused by a failed covered failed part. (I had a belt pulley cease, the belt broke, engine overheated and bursted a coolant line. They only covered the cost to replace the cease pulley and I was on the hook for the rest.
I can attest that it is definitely happening to the M276 engine.
Car is 2014 E350 with 70k miles, well maintained.
Two days ago it threw a P0301 code, engine misfire in cylinder 1.
I swapped the ignition coils between cylinder 1 and 2, still same code. I also swapped the plugs, same code.
Yesterday I took it to a dealer for diagnosis. They called today and said there is oil everywhere.
I went there to take look. Apparently the left/driver side camshaft position sensor allowed engine oil to go through it all the way into Engine Control Unit. There was lot of oil on top of the ECU where the big connector attaches.
The mechanic also said the voltage at the ignition coil for cylinder one was about half of the normal value.
Their suggestion is a complete harness and ECU replacement at the cost of about $8,000.
My question is, if I replace the camshaft position sensor and give the connectors and the ECU a good cleaning, would that cure the problem?
Has anyone tried this and did it work?
Last edited by dacia; Feb 10, 2022 at 07:17 AM.
Reason: spelling
Replace the cam position sensors. These are inexpensive and primary offenders. Also replace the cam solenoids which seem to be the secondary offenders, and not expensive in the big picture.
Clean all of the harness connectors and the ECU connectors.
These two steps will give you time to weigh further options.
Harness replacement is a DIY job if you are generally comfortable with working on cars.
Coils and injectors may or may not need to be replaced. If you address the leak sources and DIY the work, you can manage this.
Addressing this situation does not cost $14k. However it requires you to spend time, money and effort to do the work. Lots of owners on this site can help you through this.
As a point of encouragement, I had some problems about a year ago on my 2013 GL450 M278 where the cam sensors leaked oil into the harness. But my engine survived. I was lucky I caught it in time, as soon as I saw a code then I suspected the oil in the harness. I stopped driving it, found oil in the harness all the way up to the CPU, replaced the two cam sensors and magnets, and left the harness unplugged for a couple days with the connectors hanging down as far as I could get them, to help drain the oil. I removed the CPU, cleaned the oily connectors, and propped it up vertically (connectors down) for a couple days to drain the oil. I jammed pieces of paper towels into the connectors while they were draining, to wick the oil away, which seemed to work. After reassembling everything, it ran fine. I had to disconnect the connectors and CPU every few days for the next month, and re-clean the connectors as more of the residual oil migrated to the connectors. Each time was a little less oil, and eventually I didn't notice any more. It's been maybe 10,000 miles since then and no more problems. Cost: a few hundred dollars for the sensors, many hours of my time for replacing them and the repeated cleanings, a few days of lost use of my vehicle, but zero trips to a dealer or mechanic. I was lucky to catch it early, but also I was smart by researching known problems with my vehicle, being part of this great community (thanks everyone, you've saved me tons of money!!), and being willing to try fixes myself.
I just removed the ECU, I turned it up, connectors on top, and sprayed it very generously with CRC electronic contact cleaner. So much that there was maybe 5mm of liquid cleaner floating on top of the electric leads.
It looked like none of it leaked down into the ECU when I checked it a few minutes later which seemed to have confirmed my suspicion that ECU is actually water proof.
If that is the case how could it be damaged by oil "leaking into it" from the harness connector?
My other question is how to actually find out if the engine misfire is caused by the ECU or something else?
I swapped coils and spark plugs and it didn't help, the misfire stayed with cylinder 1. So other than a clogged fuel injector is there anything else that could cause a misfire, beside a bad ECU?
The dealer wants to change the entire harness AND the ECU which seems rather strange to me.
If the ECU is functioning then there is no need to change it.
Is there a way to check if the ECU is working fine?
As a point of encouragement, I had some problems about a year ago on my 2013 GL450 M278 where the cam sensors leaked oil into the harness. But my engine survived. I was lucky I caught it in time, as soon as I saw a code then I suspected the oil in the harness. I stopped driving it, found oil in the harness all the way up to the CPU, replaced the two cam sensors and magnets, and left the harness unplugged for a couple days with the connectors hanging down as far as I could get them, to help drain the oil. I removed the CPU, cleaned the oily connectors, and propped it up vertically (connectors down) for a couple days to drain the oil. I jammed pieces of paper towels into the connectors while they were draining, to wick the oil away, which seemed to work. After reassembling everything, it ran fine. I had to disconnect the connectors and CPU every few days for the next month, and re-clean the connectors as more of the residual oil migrated to the connectors. Each time was a little less oil, and eventually I didn't notice any more. It's been maybe 10,000 miles since then and no more problems. Cost: a few hundred dollars for the sensors, many hours of my time for replacing them and the repeated cleanings, a few days of lost use of my vehicle, but zero trips to a dealer or mechanic. I was lucky to catch it early, but also I was smart by researching known problems with my vehicle, being part of this great community (thanks everyone, you've saved me tons of money!!), and being willing to try fixes myself.
@oldmangrimes Great post, this is the most comprehensive DIY approach i have seen on this site to the oil in harness situation. It is exactly what I would do. It would be great to hear from you every 5k-10k miles to see how things are going re: your oil in harness situation.
I just removed the ECU, I turned it up, connectors on top, and sprayed it very generously with CRC electronic contact cleaner. So much that there was maybe 5mm of liquid cleaner floating on top of the electric leads.
It looked like none of it leaked down into the ECU when I checked it a few minutes later which seemed to have confirmed my suspicion that ECU is actually water proof.
If that is the case how could it be damaged by oil "leaking into it" from the harness connector?
My other question is how to actually find out if the engine misfire is caused by the ECU or something else?
I swapped coils and spark plugs and it didn't help, the misfire stayed with cylinder 1. So other than a clogged fuel injector is there anything else that could cause a misfire, beside a bad ECU?
The dealer wants to change the entire harness AND the ECU which seems rather strange to me.
If the ECU is functioning then there is no need to change it.
Is there a way to check if the ECU is working fine?
@dacia Oil is an electric insulator. When a film of oil coats the metal pins in any connector, the potential exists to insulate and interrupt the electric signal. Because of vibration and thermal cycling in a vehicle, the loss of electrical contact is generally intermittent, unless the oil penetration is extreme. In the early stages, this problem is correctible. If not correct early, oil may compromise the ECU circuit board, on the other side of the connector pins. This would require a new ECU, and coding by a dealer to program the ECU to your VIN.
Regarding cause of misfire, read codes and use normal diagnostic steps and approaches to isolate the cause of misfire.
Potential misfire causes:
- oil in harness
- bad spark plug
- bad coil wire/boot
- bad coil
- scored cylinder bores (reduced compression)
- water/coolant in cylinder (failed head gasket)
- failed injector
- failed fuel pump
- failed cam chain tensioner or sprockets
- failed cam adjuster phaser
- failed cam position sensors or solenoids
Check your ECU connector pins for oil. Check both connectors: harness side and ECU itself. Presence of oil can be a cause of problem (codes).
I have been following this thread with interest for some time. I have a 2015 GL350 with the OM642 diesel engine, currently at about 98K miles and with the AEM. I have searched but have not found any issues with oil in the engine harness for the OM642. I presume that the OM642 has cam sensors of similar design and that the OM642 would be subject to the same issue. Can anyone comment the the susceptibility of the OM642 to oil in the engine harness? If so, I will start some pre-emptive inspections and maintenance. Mike
I'm returning with an update regarding the oil in the engine harness and ECU in the 2013 SL63. I spoke to the independent Mercedes shop (As background on these guys, they are very nice and carry. Furthermore, from their website looks like they do service on an original 300SL gullwing and SLR, on top of many other interesting Mercedes and BMW cars). After they looked at the car, they still believe the best option is to replace the camshaft sensors and clean all the oil very well. They also found that oil reached one of the four O2 sensors (Mercedes didn't bring this up).
The mechanic said they have seen a lot of these oil in harness and ECU situations at various stages. They said my issue is in the very early stages and they have seen worse situations that continue to work fine. The mechanic said he has seen so many of these issues just in the greater Boston, MA area that he expects any day now to hear about a class-action lawsuit on this. We've had some back and forth about what to do and we agreed to talk again on Monday (I'm not in a rush to get the car back).
I'm thinking of having them replace the camshaft position sensors, the cam solenoids as well as maybe the intake O2 sensors (I assume there are 2 intakes and 2 exhausts for emissions, but I might be wrong) and all 8 injectors.
Here is my reasoning for the injectors. The Mercedes service advisors said that injectors could start leaking oil up the engine harness in certain situations. They said the cause of my oil in harness situation was dues to "porous camshaft sensors and injectors on cylinders 1, 6, 7 and 8". However, the independent mechanic said he has never seen or heard of injectors leaking into the harness. In my third-party warranty document (not CPO), it says they would cover injectors, but both Mercedes. However, the independent mechanic said the warranty will want to know about the entire issues, plus nothing has actually failed.
The other bigger issue why I want to replace the injectors is because they are now in my head as a problem. So far, every time I had a problem with my car in my head and I let it go, that problem came up... The big two are:
1) In October, I was revving the car for some kids and I heard a weird noise that sounded like a belt slipping. I thought I should get that checked, but a couple of days later (right before calling Mercedes to schedule a check) I revved the car again and didn't make that noise. So I decided not to look into it any further... Two weeks later, the serpentine belt blows, the car overheats, and blows a coolant line. Towed the car to Mercedes and the cause was a ceased pulley... Cost me a total of around $2,700 after the warranty would only cover $300 because they only cover that part that actually fails and no subsequent damage... Side note, when the belt blew, it spliced the wire harness, which I noticed after Mercedes gave me the car back. So I've been driving around for two weeks with an exposed wire harness and now I'm wondering if oil/coolant got in there that way too... I took the car back to Mercedes and they repaired the spliced wire.
2) In November, I was talking to my Mercedes Advisor about the camshaft sensors. He did tell me it would be a good idea to change them, but right now everything in my engine was dry. So after already spending $3,000 on the belt-blowing situation, I didn't want to spend another $1,000 to replace all 4 camshaft sensors. I did plan to change them in April when I was due for the B Service. Now... as you've seen, those sensors created a big issue...
Replacing cam position sensors and solenoids is the bare minimum.
Replacing O2 sensors makes sense if they have been contaminated.
Replacing the engine harness is a good idea, because this is how oil is moved around to the various points. Not terribly big dollars for parts, but requires a fair amount of labor. Best done DIY but also possible at the dealer or indy.
Replacing injectors in my view would be only if needed. Not out of the question though.
Yes, I'll definitely replace the camshaft sensors and solenoid.
I'm concerned about changing the wire harness in case there is another source leaking oil into the harness (like the Mercedes guys said it might be possible). Has anyone heard of any other source where the oil got into the wire harness, except for the cam sensors/solenoid?
Other than the camshaft sensors, crankshaft sensor, injectors, are there any other items connected to the wire harness that comes in contact with oil?
I don't have the space or the capabilities to DIY much on my car. Every idea I'll have to run it by the independent mechanic and see if he can do it.
There have not been widespread reports, or any reports I am aware of, for oil entering the harness besides the cam position sensors and cam solenoids. The MB service dept. is playing the fear card as always.
Replacing the cam position sensors and cam solenoids are dead easy for an indy shop. If they hesitate for a fraction of a second, go look for another shop. It's dead easy.
There have not been widespread reports, or any reports I am aware of, for oil entering the harness besides the cam position sensors and cam solenoids. The MB service dept. is playing the fear card as always.
Replacing the cam position sensors and cam solenoids are dead easy for an indy shop. If they hesitate for a fraction of a second, go look for another shop. It's dead easy.
Indeed, both the sensors and magnets are extremely easy to replace yourself. Not even worth driving to a shop for that.
Last edited by steh-fan; Feb 14, 2022 at 10:48 PM.
Reason: Re-read posting
Indeed, both the sensors and magnets are extremely easy to replace yourself. Not even worth driving to a shop for that.
Actually on the M276 engine the intake manifold has to come off in order to replace the camshaft position sensors, there are 4 of them. I know, I just changed them this afternoon.
The camshaft magnets or solenoids can be removed without removing the intake manifold, I just changed two of those as well, they were both leaking oil around the seal but there was no oil in the connectors.
On the other hand 3 out of the 4 sensors on the op the engine were leaking oil into the harness.
After spending about three hours changing the parts and cleaning the connectors the misfire in cylinder one, code P0301, remains.
So now I've got a problem because it's either the fuel injector for cylinder 1, the wiring harness or the ECU, hopefully not a mechanical problem with that cylinder.
People above are taking about "cleaning the harness", what does that mean exactly?
From what I see there isn't much to be cleaned except disconnecting the connectors, spraying them with CRC cleaner and then drying them with compressed air.
Which I have done this afternoon to no avail.
Is there anything else that could be done?
I would hate to spend the money but I don't see any other option than going to the dealer for a wiring harness replacement, I can't do it myself.
However if it is the ECU and not the harness then I will have spent a good chunk of money, for nothing.
Not to mention the fact that the wiring harness is on back-order from Germany.
And they don't have ECU even in Germany, according to the dealer's computer,
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