M272 fault diagnosis

[JamesG66]

Having a bit of fun and games with fault codes from my C350, which runs the M272 and hoping others may be able to help.

Firstly, about six months ago the CEL came on, I read the codes, replaced the lower (exhaust?) camshaft magnet on bank 1 and for the last 4 months it has been trouble free.

More recently the CEL came on again with the following errors:

P0015 - B Camshaft Position Over Retarded Bank 1
P0172 - System Too Rich Bank 1
P0175 - System Too Rich Bank 2

This time I replaced the upper camshaft magnet on bank 1 and reset,although writing this it occurs to me that Camshaft B is the exhaust and I've replaced the magnet on the intake. Can anyone confirm?

Anyway, the CEL came on again, but this time just the "Too Rich" codes. So I pulled the MAF off, cleaned it with some proper cleaner and put it back on. Interestingly that's made a massive difference to startup behaviour. Before, when cold the idle was lumpy for the first ten seconds, but now it's smooth right from the off.

Now, a few days later, the CEL light is on again though and this time it's giving these codes:

P0015 - B Camshaft Position Over Retarded Bank 1
P0366 - Camshaft Position Sensor "B" Circuit Range/Performance (Bank 1)

Mileage is 72k and my engine is definitely in the danger zone for balance sprocket issues. Performance, smoothness and fuel consumption are all normal.

It's easy enough for me to replace the CPS and the magnet but is this just balance shaft issues presenting themselves? I would have thought the timing would be out on both banks if the sprocket were worn or is that wishful thinking. I would happily swap it out for a W204 C350 petrol but they never come up so I'd like to get it sorted.

Thanks in advance.

 

[JamesG66]

Update:

I swapped over the camshaft magnets so now the new one is on the exhaust cam, and reset the CEL. It came back on after about 40 miles.

However code P0015 is gone and I am left with code P0368 (typo in previous thread when I said it was P0366)

I am now tempted to replace the camshaft position sensor, but despite being a simple hall sensor it's £133+VAT from my MB. My local dealer has one in stock however.

Anybody got any other suggestions before I go down that route?

Thanks

 

[costa]

I am having the same problem with my EML on intermittently and has been for two years but still a pain. The rogue cam solenoid has been replaced sometime ago and then swapped for the other cam solenoid to check but EML still coming on. Engine is running fine so I am at a loss to know what the problem is so is my mechanic and dealer. Although as you would expect the dealer can sugesty all sorts of expensive solutions. On the balance shaft issue I am reliably told the if your engine number is more than 2729..30..468993 then you have a modified/improved shaft sprocket and it shouldn't be the problem. Should have said that the fault code has been delete several times.

 

[anderoo]

Newbie here (I've just posted a quick intro in the new member's section), but I am having the same issue. It's slightly reassuring I'm not alone. I have a 2006 C350 and about a year ago the camshaft solenoids were replaced and all was well until just before xmas. A P0015 code appeared and I took it to the specialist I use (in Reading) who initially thought that as the solenoids had already been replaced it may be the balance shaft. Once they'd done the diagnosis they ruled that out (although it is in the range for that) but weren't able to pin down the fault, although they said that if they fed in a bit of false data it looked very likely to be a worn sprocket elsewhere in the timing gear. They reset it all and told me to run it for a bit more, see if the fault reappears and then come back.

I've done that - it has reappeared and been deleted a couple more times now - and now the light is back on again so I'm taking it back to them this week. The car runs fine - no symptoms that I can tell.

So it's not the balance shaft (yet ), it's not the solenoids, but the timing is ever so slightly out for some reason. Hopefully they'll be able to pin it down - I'll report back either way in case it's helpful. If it's not the other sprocket, I wonder if it's just a dodgy sensor somewhere? I HATE having that orange engine light on!

Edit - forgot to say, mileage is 75k.

 

[rorf]

Unfortunately it will always be the balance shaft sprocket, bad engine

 

[mbenz1]

On the balance shaft issue I am reliably told the if your engine number is more than 2729..30..468993 then you have a modified/improved shaft sprocket and it shouldn't be the problem. Should have said that the fault code has been delete several times.

I remember vaguely, one member on this forum bought a CLS 350 with the 'hardened' sprocket and got caught in the sprocket wear issue at 40k miles (if I remember correctly). Its a gamble with these engines IMHO.

Sent from my GT-I9505 using MBClub UK

 

[anderoo]

Unfortunately it will always be the balance shaft sprocket, bad engine

It isn't - I wish it was, then I could get it fixed and forget about it. That will happen at some point, but this fault is something else.

 

[grober]

There are two protagonists in this engine timing marriage- sprockets and chain-- something has got to give- if not the sprockets-- maybe the chain??? IRRC when the fault surfaced initially in the US Mercedes' initial response was to update the software which monitored timing discrepancy to expand the error limits before the warning light came on. While not a cure it did prevent the warning light from coming on for several thousand miles more?

 

[anderoo]

Apparently, if it was the chain, the timing would be out in both directions. So unless it's a faulty sensor somewhere it's likely to be a sprocket - but probably not the balance shaft sprocket.

The merc specialists who looked at mine said they'd never seen it before (and they've seen plenty of dodgy balance shafts and solenoids) so it looks like a pretty rare problem (lucky me!).

It would be interesting to know if any other indies on here have any ideas?

 

[anderoo]

OK, so apparently this needs a new exhaust camshaft and piston. Hope that helps...

 

[JamesG66]

Update from me. I bought the camshaft position sensor for a crazy £144 from MB and fitted it over the holiday. Codes cleared, and no sign of CEL yet but I haven't done many miles.

A new issue has come up though which pre-dates replacing the camshaft position sensor but is getting more noticeable, which is a strong smell of fumes in the cabin. It's post combustion, so am thinking exhaust leak somewhere.

 

[JamesG66]

OK, so apparently this needs a new exhaust camshaft and piston. Hope that helps...

Keep us posted if that fixes it. Presumably replacing the exhaust camshaft, although cheaper than the balance shaft, still isn't cheap?

 

[grober]

Update from me. I bought the camshaft position sensor for a crazy £144 from MB and fitted it over the holiday. Codes cleared, and no sign of CEL yet but I haven't done many miles.

A new issue has come up though which pre-dates replacing the camshaft position sensor but is getting more noticeable, which is a strong smell of fumes in the cabin. It's post combustion, so am thinking exhaust leak somewhere.

If its exhaust fumes you are smelling then more likely to be a leaking or cracked exhaust manifold sending fumes into the engine compartment rather than a leaking exhaust where fumes are more likely to be swept away by airflow under the car?? May only happen once the engine is warmed up. You might be able to hear a bad exhaust leak by lifting the bonnet once the engines warmed up/

 

[anderoo]

Keep us posted if that fixes it. Presumably replacing the exhaust camshaft, although cheaper than the balance shaft, still isn't cheap?

Yes will do. And no, it's not cheap! It's going to be about £1,100 - happy 2017 to me They seem confident that they've finally pin-pointed the problem, so this ought to fix it... it's not a common problem apparently, but given the difficulty in diagnosing it and also that the generic OBD code (P0015) suggests it's just a faulty solenoid, maybe it's not quite as rare as it appears, maybe a decent number of these just go undiagnosed.

For those who understand this stuff more than I do, what do you reckon would be the cause of this, if anything?

JamesG66 I hope that does fix it for you, keep us posted. I cleared my code a few times before now and it always came back - sometimes straight away, other times after different amounts of time/miles (including a 500 mile round trip to the lake district over xmas).

 

[anderoo]

I've just got my car back, it wasn't the camshaft that was replaced but the sprocket and actuator on the end of it. The sprocket wasn't worn but had failed internally - a pretty rare fault apparently, but probably also quite often misdiagnosed and/or ignored. A pretty expensive one too as the part is over £500...!

 

[JamesG66]

Good to hear that your issue has been solved and as you say a likely candidate for mis-diagnosis. Out of interest who did you use for the repair?

From my end the new sensor seems to have solved my issues and I've also traced the source of fumes to the camshaft bore expansion plugs at the rear of the engine, so it was oil not exhaust I was smelling. Thankfully a cheap and easy fix.

 

[WG M-B]

I've just got my car back, it wasn't the camshaft that was replaced but the sprocket and actuator on the end of it. The sprocket wasn't worn but had failed internally - a pretty rare fault apparently, but probably also quite often misdiagnosed and/or ignored. A pretty expensive one too as the part is over £500...!

It's not common but the sprockets do fail

 

[anderoo]

I use Star motor services in Reading, they're the closest indie to me here in Oxford. I think they post on here sometimes.

 

[anderoo]

Ha - this may not yet be over. After the first repair the CEL came back on after a few cycles with the same code, and the garage reset it all (apparently the adaptation hadn't taken following the fitting of the new parts). It's done 300+ miles since and I'm now seeing pending codes for the same fault, although as yet no CEL. I'm worried now that the repair didn't fix it after all. Or maybe the adaptation just hasn't taken properly? The repair was done following diagnosis on STAR by a reputable indie who I've used before and have no reason to mistrust.

Looking around the web, it does seem that some unlucky people suffer from recurring P0015 codes on various makes of cars, and very little in the way of resolution. Some say that cold weather and old oil is enough to trigger it. I am due a service and it's freezing, so perhaps these are contributing factors - but it feels a bit like clutching at straws.

Also, I'm due an MOT in a month and am concerned that it it's not resolved by then it might mean a fail. If you clear a CEL or pending codes before an MOT presumably they will notice that and fail it?

Any thoughts or encouragement welcome...!

PS JamesG66, apologies for hijacking your topic. Is yours still OK after changing the sensor?

 

[JamesG66]

No worries, all M272 talk is useful for sure. Sorry to hear that your problems are not yet over.

Regarding my car, yes, all is fine since changing the sensor but something you may want to check on your car is the fit of the airbox to the MAF. While I was investigating my fumes issue I pulled the airbox off to have a good look at the camshaft core plugs. When I put the airbox back on but I didn't seal to the MAF correctly (I recently replaced the seal and in this cold weather it's stiff) and within 10 miles it had thrown up the P0015 code. Next chance I had I fitted the airbox properly, which took quite a bit of effort to ensure the airbox seal fitted over the MAF uniformly and it's been fine every since, about 500 miles worth or so.