Next inspection, use your MLK 1.2 male, you have the male one too right ?
Test for friction fit at all the positive FEMALE pins of the magnets at the ECM connector wire harness side.

M connector, which is the biggest connector with most pins.
Female Pin 54 is the Bank 1-Right bank intake magnet, the suspect.
The rest you see the wiring diaghram.

Have fun.

 

Dear S-Prihadi,

We are all in debt to you.

I took a "family day" today, did not do any investigation.

Let me go back to my 9.9VDC and 3.3VDC Test to explain: I do not have a good "spicing method"..am improvising with what I can find.

I disconnected the magnet, magnet was off the car, just freely sitting on engine.
With Engine off, but key in running position, hence ECU etc active,
The connector from the harness - I brought my DMM and measured each Pin on Connector for VVT magnet vs Ground (Engine).
Result as you know, were 9.9VDC and 3.3VDC: What I saw was important that the results were consistent across all VVT magnet connectors, hence I don't see any break in wiring (seems like far remote possibility).


The 3 videos of Rattle Noise.

Third last video shows the rattle in early stage, I think I had some of that, and I attributed that to noisy engine.
Then just a few days ago I heard the 1st Video rattle, that lasted 3-4-5 seconds, loud knocking.

What is that noise? Phaser or Chain Tensioner?

I had the following in mind:
Mark the phaser and the center bolt / center of phaser. Then, Rotate the engine to try to spot the phaser moving- but cam not moving (center of phaser not keeping up with outside). This may - after 3-5+ revolution identify Phaser as faulty, or not.
Also phaser may "puke oil", may not. If it does, it's indication it is bad.

Next take out Chain Tensioner, measure it's extended length: Spec says minimum 74.5mm (I believe). If it's less then 75mm needs replacing. If it's below 74mm it is maybe the source of rattle?

Then, take off Phaser, see if Cam and Cam timing Wheel are aligned : does the scribed mark align? If not, sadly cam has to be changed. P.S. I am surprised that nobody re-aligned the cam-timing-wheel and tack-welded it to the cam? Or pinned or some other method.


To remove the phaser, I have to hold the cam. Can I hold it without taking off valve cover- somewhere?


NOTE: I took the car to local mechanic, who has experience with these cars, but is not specialized in them. I see regularly various ML/GL E/C S class, Mercedes coming, they all share the M276 various years.
I've seen him do M157 services, big ones included like water pump and cooling lines and thermostat etc.
However he is not focused solely on Mercedes, so unless he came into an exact issue he may not know when was chain updated, or some other detail, unless he looks it up.

His first concern was stretched chain, due to rattle. I had some hard time convincing him that 2013/2014+ M276 has updated Chain, and Check Valves, and chain is not the culprit.
Then he said to inspect the timing marks through cam -sensor holes, and they were close- or right on ?
He never believed that it was Electrical Problem as P2088 would have you believe...he was always sure it was "timing issue".

As you can see from the test of the VVT magnet connectors, it is unlikely that it is indeed an electrical short to ground or open circuit: all measure same, and while engine was running we were moving the connector wire/pig-tails to stimulate it, to see if engine will react- if we manage to break electrical connection. Nothing happened.

the shop likes to replace cam along with phaser, - the young mechanic said it is recommended even if cam wheel is aligned: to me that sounds like waste of money as cam is expensive, and I hope cam-timing-wheel moving is rare occurrence.

Hope my proposed mechanical inspection makes sense.

Any suggestions, comments?

 

Damn it damn it damn it , brain fart moment.

I mistaken Z7 wiring group as negative/ground, in fact Z6 is the ground. My most sincerely apology. I have to correct all I wrote wrong in this thread after this, so that no one will make mistake...dugggghh.



My brain memory cell is failing, it was only 4 years ago I was messing around with Z7 wiring group... to make this "Relay Tree List" for faster troubleshooting.





---------------

So magnet connector pin #2 is power from fuse 23 or 24, the pin #1 is the pulsed PWM using ground wire aka negative switched component.
How could I forget this....double dumb-azz me.

----------------

My eyes fooled me too.
It seems I made a mistake for which one is pin 1 and pin 2 on my photo archive of test.

I will update...........

 

DELETED - Brain fart moment.

Will update

 

The loud knock knock sound is from VVT oil vane hitting the VVT housing end stop. This is Chapter 11 issue, I mean expensive.
Usually it is the locking pin which failed.

See below from Master Tasos :

Oil vane :

.




.



B is the VVT cover or part of the VVT assy, which has hole for A pin. The hole got enlarged due to wear and tear and the A pin can come out of the hole un-intended.




A pin also lock the oil vane, at the hole below I labeled C



So it is strong metal against metal KNOCK sound at 500 times a minute or 8 times a second, at cold start where crankshaft RPM is 1,000 for a few seconds.
Chain sound is "mild", I mean not a KNOCK KNOCK.

.

 

DELETED - Brain fart moment
Will be back

 

Okey, Brain Fart moment over.
This is not the first time my eyes fooled me.

Anyway I did the test again to compare.

To be clear visually :

Pin 1 of connector of magnet from wire harness is to ECM PWM negative switched, so this is negative.
It so happened my wire kit uses black wire cable for Pin 1.

Pin 2 of is from fuse 23 or 24 or positive, depending on exhaust or intake magnet we want to test.
Pin 2 on my wire test kit uses RED wire, good.


Tip: On Hirschmann SealStar connector above and below , at least up to 3 pins models, the rounded side is always PIN 1.






======


I redid the test just to make sure no more brain fart moment.


Ignition ON, engine OFF
Magnet not connected.
DMM positive to pin 2. DMM negative to pin 1. I get 9.x volts.



Ignition ON, engine OFF
Magnet connected.
DMM positive to pin 2. DMM negative to pin 1. Result = 4 to 5 millivolts




Ignition ON, engine OFF
Magnet not connected.
DMM positive to pin 2. DMM negative to metal ground, engine lift hook. I get system voltage 12.54 volts. Is this where you get 9.x volts ?
This has to be full system voltage. Because Pin 2 is direct from fuse 23 or 24. Yes shared by many sensors this fuse/s.





Ignition ON, engine OFF
Magnet not connected.
DMM positive to pin 1. DMM negative to metal ground, engine lift hook.
So this is reading ECM PWM negative output ( not pulses unless engine is ON ) against true chassis ground, at engine metal lift hook. 3.4 volts




Now, if indeed your DMM reading of Pin 2 to ground is only 9.x volts, and for all 4 magnets ????............... you may have problem at splice or X26 no 1 intermediate connector.
The big black+grey 14 pin or so.

This is where and how fuse 23 and 24 is wired/routed for M276.9 3.5NA
-------------
Z7/35z2,shared by many components using splice (parallel ) and goes to big connector X26 #1 pin 7 and then to Front SAM N10/1 connector 3M pin #6 to fuse 24.
Z7/38z1 , shared by many components using splice (parallel ) and goes to big connector X26 #1 pin 5 and then goes to Front SAM connector 3M pin #5 to fuse 23.
-------------

X26 no 1 for ur engine, In front of LEFT BANK




It looks like this : This is from my car, yours would be very similar


.



More upstream than X26 no 1 is the Relay N which is basically a "connector".
Relay contact points can get pitting.

.


.





.
Go and try the 9.x volts again to re-confirm.


.

 

S-Prahidi,

Thanks, that connector on the front you pointed out, has been a bit of my concern, but all 4 VVT Magnet harness-side connector show same,,- it is relative reading, you had 9.0 I had 9.9 VDC, you saw 3.4 I had 3.3 VDC, noise level .What is important is that they can all not go bad at once and it the did- there would be 0 VDC or open circuit - something other then reading that repeats itself.

Let's also take into consideration, P2088 via AutoLink may be "sort of accurate"..who knows.
Indicato where to look.

What is for sure true,
1st car had an episode 1st time ever of going into rough running mode. Drove it home 1 mile - parked. P2088
2nd I went over everything, restarted car, drove ok for 2 miles or so, went again into rough running mode, Drove home. P2088
3rd I went over everything again, and more, drove ok for 2 miles or so, went again into rough running mode, Drove home, P2088.
4th I went over more, swapped out Exhaust VVT Magnet (thought it was exhaust cam- my bad misreading P2088), started the car..started knocking 3-4-5 seconds. I never heard this before. And went into rough running mode immediately. No driving.
5th Tested Magnet voltage/powered magnets in primitive way with VDC, got all to read same, all VVT magnets work, and checked timing marks: seem close enough (1-2mm off or not). Now if I start the car, I hear clutter like chain tensioner or something, and rough running.

IN concluding, total driving distance 6-7 miles, for point 1 to point 5.
during this time, car went from starting to run rough after some driving to running rough all the time.
It also had 1-episode, or maybe 2 - episodes, of hard knocking noise coming on start up for 3-4-5 seconds.
And on every start up it clatters a bit, until it settles running, (say like chain tensioner that took a while to pump up oil to keep chain under tension? Or maybe Phaser can do same? And it runs rough...constantly.

So whatever failed was little more intermittent, now it is constant, making it marginally easier to identify.

I doubt it is electrical problem.. but I don't know.

I think I should take out Cam tensioner on B1, and see if it is 74.5mm or longer.
Maybe it comes out totally failed.

Then I should take off Sphere on Intake cam on Bank 1, - see the cam - degree wheel alignment and maybe the phaser will come out being somehow obviously broken? I never seen broken, nor do I know what I am looking for in phaser once it is removed.

 

UPDATE, the car works.
No parts changed.

I walked by the garage today, to inquire if any news, and they said to go drive it. It's awesome as it was.

turns out during "reassembly" of VVT actuators, - Intake was put to Exhaust, Exhaust (Old one I put there) away into the Bag. New one that I took off Exhaust and kept in bag was put onto Intake.
During assembly, it was noted the Intake VVT magnet required a bit of finessing to fit.

The ignition coils plugs and all connectors were checked, but nothing found, as well.

Once assembled like this, car went back to normal on Saturday.
I did not go to garage as I felt I was spending too much time micro-managing, I had to give them the space..


It was cheap, and it was honest. Amazing honestly, I was ready ..for big $$.

The consensus is that Mercedes is nowhere near as bad as it may appear, but people tend to throw parts at them.
Most run flawlessly to advanced age.

I have my confidence in Mercedes back, which is good as it has been part of the family since I was a kid, and we have 3 currently.


Thank you S-Prahidi and all others, for your heartfelt attempts to help me out and to educate the wider community how to troubleshoot, rather then throw parts at a problem.

Cheers

 

Glad to hear today engine is OK

But please explain clearly what you meant :
"turns out during "reassembly" of VVT actuators Intake was put to Exhaust "

"During assembly, it was noted the Intake VVT magnet required a bit of finessing to fit."

Actuators = magnet ?

Or VVT actuators is the complete VVT sprocket/phaser like below ? ( less oil valve ). Dang why is my image not sticking ? ( add: now image is available )
or use this Link :

Amazon

Amazon

If magnets : all 4 are the same, you can swap all you like.

If complete vvt sproket/phaser, yours never been touch so far...yes ? You told us you are considering to replace the bank 1 vvt sprocket/phasers but you have not confirmed it yet.

 

Just vvt magnets swapped in/out

removed and same ones reinstalled

so nothing changed out

simple

 

, probably you did not plug in properly the connector when you are the one doing it .
My boost controller is the same 2 pin connector and is extremely stubborn to get it to "click". Maybe the seal inside flipped or something.

 

I plugged originally, then unplugged, replugged, and again, both the B1 Intake and Exhaust, and did also clean up with Electronics Spray cleaner.

I explained in the start that I tried to resolve the issue - being P2088 - suspecting electrical issue - by ensuring all electrical connections were perfect.

in the end, it was somehow the fit of Intake Valve VVT Magnet driven solenoid: it is a fool proof fit to an extend, 3 bolts for clocking, tight-ish bore for concentricity, and flat face to seal for perpendicularity. Yet, somehow did not engage Phaser/cam correctly.

It was purely a mechanical issue, despite what P2088 would have us believe, like AI lying and making up stuff, ECU sometimes is not programmed for specific situation nobody thought of.

Cheers.

 

This makes very interesting case study.

I agree there is no way the magnet does not sit well , unless the o-ring slipped out of the groove and cause a gap.

On the other hand, think about it, scenario : the magnet is assumed to not sit well, its electrical consumption is out of the pattern and ECM detected it as P2088.

FYI : FRONT SAM/ REAR SAM : The indoor or door or trunk 5 watts T10 incan bulb is detected by amperage consumption range, if you swap to low amperage LED bulb, soft DTC will be produced.
If too large an amperage say a 15 watts load we tap from it , driver will cut power and declare short circuit type DTC.

I wonder if the push valve of the oil valve the magnet is pushing has grime/dirt and cause friction , electrically causing more amperage than typical, will the ECM detect
it and produce another DTC for magnet or produce DTC for cam degree not achieved ?

 

Hello S-Prihadi.

I am quite experienced mechanic-enthusiast, who at one time was professional, and am naturally inclined. My arms/hands are calibrated torque wrenches.
Am mechanical engineer- semiconductor capital equipment.

The M276 M157 are new to me, hence careful approach and discovery process. But I understand how to contain a fit, and I feel/know how to assemble something.

We will never know what was the root cause, but the important lesson is to take every CODE with a grain of salt.

Code is note of a situation that mercedes engineering department considered possible.
There are going to be situations they either did not consider or did not think were very likely, or a situation that is a combination of 2 or more factors.
So code is indicator, rather then hard fact.

Another lesson is that even experienced assembler can seemingly assemble something to fit, look, and even "seal" as it should, yet, the engagement inside is not right.
This is especially true when doing it first time, the specific assembly: any assembly can have characteristics that you discover after you disassemble and reassemble it a few times. You get to "feel" the right and "not right" feel.

Don't dwell on it, just open the mind that it's important to follow intuition, not only code, and inspect the basics: Open cam sensors check timing alignment, listen for rattles that are tell-tales, check with simple volt-meter the connectors and actuators/solenoids- without resorting to exotic special equipment - if at all possible: quicker cheaper and more accessible to all. And take stuff apart if in doubt that it was assembled correctly.

Deep dive can follow if simple inspections do not yield results.

 

You being a competent DIY make this P2088 all the more interesting due to it keep being triggered while electrical connection wise all good.
I agree, DTC explanation can be misleading, but if the same DTC keep happening, we know something is triggering it. The repeating pattern is what made me find it interesting.

I did trigger P208800 and others for my own giggles, but engine is OFF. I deliberately place a 130 milliamps short circuit on the ECM driver output for the magnet of BANK 2, intake and exhaust.



If you previous suspected VVT rattling is now gone, this case study may mean a lot more importance.
This could mean : a not properly seated misbehaving magnet may cause the VVT oil vane lock to be released un-intended....that is my guess.

Intake camshaft VVT-s, during cold start ( my 30C cold start ) , is programmed to stay locked.
Exhaust camshaft VVT-s, 5 seconds after engine COLD start, is programmed to start its activation for X seconds till engine deemed warm enough.
5 seconds is also the typical time the engine need to build up maximum oil pressure after engine start.

VVT activation is the same as magnet actuation or vice versa.