jg.abaitua

Having some problems with a S212 E350 CDI:

• Engine OM642.852
• Transmission 722.903
• 358.600 kms on the clock

Always has shown some CAN problems that practically only affected to the COMMAND head unit. That from time to time switches off itself, and is not showing info on the Instrument Cluster, neither manageable from Steering Wheel buttons.

Other CAN communication problems showed from time to time but not affected the driveability.

Some months ago i had a unrelated problem with the oil filter gasket that ended in low oil pressure and damage to piston 1 rod and an engine change.

Engine was replaced with a very good looking (and in theory 82k kms) same code one.

Fired and started with no problems just after purging fuel rails.

Transmission oil was changed during the engine replacement, as some oil was lost from the Torque converter when dismounting.

Since the first test drive engine runs in some kind of limp mode protection which behaves showing less power that it should and changing gears at 3000rpm, no manual changes working, and diseggaging torque converter when the accelerator pedal is lift (like if you press the clutch on a manual car).
Already experienced this kind of “limp mode” some years before with a failing EGR valve. So i quickly recognised it.

Second day after engine replacement, car battery showed unable to start, and as it has been stopped for some months, i replaced it with a new one.

Just after replacing the battery car started working properly as it has always. Showing plenty of power, changing gears according to accelerator pedal movements, obeying the manual gear change levers, etc. But it doesnt lasted long…

Now after battery replacement, car works properly sometimes, and not others.
Usually runs good then after a while, can be 1 minute or 15m, it starts to fail behaving the same as before (no power, unable to manual change gears, auto changing only at 3k rpm).

Making some test drives, i thought that the limp mode stars when the ESP module show a CAN bus communication ERROR DTC, but not sure, just as a starting point.

Then started focussing on CAN Bus errors, so analysing and testing found all this to ve very frequent (although they also were before replacing the engine):

• IC A1-> U014787 Communication with the control unit 'Head unit' has a malfunction. The message is missing.
• MFK A40/11 -> C14687 Communication with the central gateway has a malfunction.
• ESP+ N30/7 -> 620800 The CAN message from control unit 'CGW [ZGW]' is faulty.

Punctually:

• CDI N3/9 -> 123900 The boost pressure is too low.
• ESP+ N30/7 -> The following fault has occurred: The control unit has rejected the diagnosis service requested by XENTRY Diagnosis. Error details: MCDError: <Undefined> (0xd04f) VendorCode: ChannelManager: 03029: ECU responded with a refuse message to the init message [3029]

As read on many threads before and know that CAN power distributors were prone to failure, i replaced the four main ones (forgot the cinematics one, i’ll replace ASAP).

• A0045468440 DYNAMICS CAN H X30/28 5x2/1x3PIN
• A0045468040 DRIVER CAN B X30/33 13x2/1x3PIN (interior RIGHT)
• A0009820212 CHASSIS CAN E X30/30 12x2/1x3PIN
• A0009820012 DRIVER CAN B X30/32 12x2/1x3PIN (interior LEFT)
• (pending)A0045461040 cinematics CAN G x30/21 5x2/1x3PIN

This made no difference to the engine problem, neither to the audio command unit problem.

Now searching for other possibilities, i’m posting this message, so to try to get some help.
Maybe the FrontSAM/CGW? Maybe the ESP module? Maybe related to the low boost message on CDI module?

I also did a diagram of the affected CAN Busses showing in pink the affected modules to try to find a point of relation between them. Attaching it.

XENTRY, Vediamo, SD C4, etc available for troubleshooting.



Can Buses Diagram


My apologies for such a long message…

CaliBenzDriver

I am in the middle of something, here are some pointers:
It's a nice long list of issues but not real bad overall... let's focus on your random limp-mode before anything else related to CAN-B.

What is doing limp-mode: engine or tranny??

Have you cleaned the footwell GND on both sides?

Have you done chassis reboots?

Have you checked batt voltage while car is having issues?

Your solderless ESP is reporting some issues but I don't think it can trigger limp-modes quietly!

Your boost fault may be all that's bugging your diesel ECU.


[ESP + F-SAM/CGW ] are always powered module... these 3 positively like chassis reboots.


Check the basics and find how to fix the regular diesel boost fault.

jg.abaitua

Not sure, because both of them behave badly, and no one shows limp mode as active in the "actual values" tab of xentry.
When failing, engine does not pull as expected, and it also cuts power just before changing gears. At 2800rpmish
The tranny only changes at 3k rpm when driving normaly it used to change at 2k rpm if driving softly. And of course rpms stay engaged with the wheels, not droping to near idle when releasing accelerator.
Not obeying the +- levers to change gear is another sympthom.

Did with the driver side, more checking than cleaning.
But all the car is very dry, clean, and not rusty. More when comparing with other cars i've seen in this kind of threads. I live in Madrid, Spain, so not close to the sea, and relatively hot place.
I think i made some pictures if you whant me to show.

How can i do that? Never heard of it. Can you please elaborate?

Xentry is showing 12.2~12.4 some times and 14v other times. Always supposed its related to the "BlueEfficiency" that disconnects the alternator depending on battery needs. Doesnt it?

Any advise on reviewing that issue? Intercooler pipes?
When the car works, it pulls as it should (at least from memory it feels).


Thank you very much for your time.

CaliBenzDriver

to wrap the above intel gathering...
90% chance you can focus on getting an exhaust pressure sensor shipped to your door step en su calle.

It's your engine protecting itself. Tranny can have similar weird behaviors in limp-mode.

Whatever you do, plug battery to a CTEK float charger as much as convenient.

Chassis reboots are full power down. All batteries disconnected 20mn. (donot short out your leads ).
This resets all modules that are always powered. CGW/SAM/ESP.

Crazy COMAND is likely internal loose pins surgery needed for top money: 500 to $2000.

jg.abaitua

Hello,

Do you mean replacing the exhaust pressure sensor on the car or getting some tool to check it?
Will forcing dpf regeneration help? for sure it hasnt been done for some months, as the car has not run for long enough, neither used at all.

I've gone over other threads were you worked with people on analysing the voltages and charging status, and electric consumptions. Do you think i can also have that kind of problems?
My battery has always behaved as expected, or at least not getting drained as far as i know.

OK, i'll try disconnecting all batteries (my car also has the small one behind cockpit) for 20min.

About the command, i'll focus on it later, or maybe never... thank you!

Rickman30

If you are familiar with automotive lab scopes, this is the best option for clearing up can bus issues. Being able to see a bad signal is the first step. Once you’ve Identified the affected can signal, a wiring diagram to see what is on that particular can line. From there you can determine which modules were affected, moved, possibly unplugged during the engine job. Either a can line is damaged or a module is unplugged.

Pine Hollow Auto Diagnostics, Bernie Thompson, Super Mario Auto Diagnostics are a few that can help if you get stumped.

Scope is the only way to identify, verify fault, and verify repair when electronics are concerned.

jg.abaitua

Being a computer engineer, and having read about CAN a lot, i think i understand how it works, but never tried on getting deeper and diagnosing the actual signals with a scope rather than just checking with a multimeter.
Can you recommend me an automotive lab scope to start with?

CaliBenzDriver

Now that you know the source of your main engine issue, you can focus on fixing it.

This has to do with your diesel exhaust sensor.

Find out what it takes to get that working reliably. New sensor may or may not bring relief to back pressure issue.

jg.abaitua

CaliBenzDriver, Can i know which of my comments made you so sure that the problem is related to backpressure in the exhaust, or the pressure sensor, etc?

I'm going to the car right now and will try to check everything related to the pressure sensor, force the dpf regen, etc.
Will update later today.

Thank you!

CaliBenzDriver

You've had the car worked on and now have an overwhelming fault collection plus a random limp-mode.

I've prioritized your list of issues to focus on the top one first.

Every issue can be worked on yet I think it's best to fix the engine before the radio.


You clearly have multiple unrelated issues. For simplicity we can not fix all at once.
Once the engine is reliable again then you can decide on your next repair objectives.

Rickman30

A good four channel PICO is best, you can occasionally score a good used one. PICO has the best support too. Plus you can send a capture to someone and get an opinion on it, which helps. There are also many who share "Known Good" captures which also are invaluable.

The other would be a used Snap-on Verus or Modis. The OBD is useful, but I've never had good luck with the regular scan tool portion, Xentry, Autel, and Launch are better.

If inexpensive is your choice, here's a good one, the uScope found on asewave website. https://www.aeswave.com/uScope-Basic-Kit-p9621.html

jg.abaitua

Yes, of course, just asking about the clue that pointed to Exhaust Pressure Sensor failing... or showing a fail elsewhere...

Well, went to the car, plugged the xentry diagnosis and at first start the engine behaved in limp-mode.
Diagnosis showed this:


The Exhaust Back Pressure value was fixed at 4734-4733. Opened the hood and checked the sensor connector and hoses. All firm. Fidled with them, and tapped on the sensor. No variation.
Drove the car, no variation.

Stopped the engine to start the forced regeneration of DPF. It showed a failure. Tried several times. Always this same error:


After that engine stop. Started again and BackPressure value went to normal and car drove properly, without limp-mode. Although the soot values went to 0, what i can not understand.


With the engine running properly i took the highway while monitoring the exhaust backpressure value. Car didnt went to limp mode in about an hour of highway (although other times it went to limp-mode while driving, not always after engine stop-start).

Stopped for a while, and after restart, the issue showed again, limp mode and very high value on the sensor. Windows clock showing timelapses.


Drove for a while and stoped/started the engine (this used to reset the limp-mode and return to normal fuction) several times until it returns to proper running.
When i was about sure that when sensor was showing ~4700 the limp mode whas triggered, car started to run properly with the backpressure sensor still showing 4738.

Anyway this morning i ordered another sensor, and hopefully tomorow i'll be able to replace mine.

¿Any advise?

CaliBenzDriver

wear gloves!

S-Prihadi

358,000KM...WOW !!!
If your CAT and DPF is still good and not partially clogged, it is a miracle.
If all the oxygen sensors at the CAT and differential pressure sensor at the DPF and NOX sensor is still good, double miracle.

Is there a way to Tee the differential pressure sensor to compare it with manual gauge ?
It look very do-able to Tee ( A & B ) as per video of E350 I seen. You need the special pliers for such Clic-R-Clamp ( C)










4.7 BAR back pressure is CRAZY, if indeed it is true.
I never mess around with any diesel engine with a CAT and/or a DPF, my marine engines even up to 2009 does not need emissions devices like cars.

When electronic pressure value is a suspect, always use known good mechanical gauge to verify.

jg.abaitua

Just replaced the exhaust pressure sensor (like in the video), but the issue is still the same. Didn't had time to troubleshoot today. I'll during the weekend...

I'll verify the electric values the sensor is giving... but it's not believable that it shows 1400, and just restarting engine, showing 4700... So although the CAT and DPF for sure are not like new after 12 years and a lot of kilometres, shouldn't be what cause the limp mode, not directly at least.

CaliBenzDriver

The new sensor shows the same exhaust pressure numbers in the ECU. We trust the sensor so something is physically causing unexpected pressure...

Can you follow Xentry guided troubleshooting from the current faults?

¿What can cause Diesel exhaust pressure to plummet?

Rickman30

Here's a good video on diagnosing issues, maybe not your issue but the methods and wisdom is.

Rickman30

Here is another on can testing without a scope,

Rickman30

And another for diagnosing can. Please pay attention to the methods used, remember the "Parts cannon" just wastes time and money and can introduce more problems, sharp shooter is being able to prove the part is bad and proving repair or fix.

Rickman30

The first video is Bernie Thompson, He also teaches auto diagnostics, has hour long sometimes two hours video classes but geared for working technicians. Well respected titan in the industry.

CaliBenzDriver

Rick, do you want to scope some of the CAN bus signals?

It's time consuming to get good scoping conditions and very easy to miss root-cause.

Ignition coil wave form analysis is a great way to troubleshoot marginal misfires. In the end "all coils" must go anyway, right?

Rickman30

I believe in the Pine Hollow Auto Diagnostics video, Ivan has some good and bad CAN scope captures on the PICO.

jg.abaitua

Still investigating about the exhaust issue rather than CAN bus, that will go just after.

I've been missreading for some days. Or missthinking... My apologies.
When you talk about the exhaust sensor, i was always thinking about the differential pressure sensor. The one with to pipes plugged to.
Yesterday i was following the wiring schematic just to find theres a exhaust pressure sensor (plugged directly to the engine, near the EGR, just above the exhaust connection), B60 in Mercedes part naming, and not B28/8 (the differential pressure sensor).


Marked red in the picture, and Part Number A0091535228.

Did some tests and with the engine idling, (this time not failing) the sensor giving a normal value of about 1300, if i manually unplug it, the value goes to the same 4734, as when it starts to fail during driving. And also the servo marked in blue, moves up and down as i plug or unplug the connector. What does that change? turbo geometry?

Also the Xentry troubleshooting mentions that when unplugged the value will go to 6000hPa... not in my case, always 4734 when unplugged, or sometimes while driving:





Is this the sensor you're referring to? instead of the differential pressure exhaust sensor? that measures before and after the particle filter what made my confussion.

As i replaced the engine and dont know the real status of it, i'll replace this sensor with the one from my engine, that wasnt behaving like this, as far as i know.

jg.abaitua

Waited for some days to do enough testing, but after replacing the exhaust pressure sensor (B60), engine never went into limp mode again. The sensor on my old engine, even being older than the one on the replacement engine still works as expected.

Thank you very much, CaliBenzDriver, and all the others that replied!
How did you know the "low boost" should be related to exhaust pressure? i was fascinated!

Time to move on to my can bus problems... i'll start by phisicaly checking connections of all the modules that used to log failing communications (COMMAND, Instrument Cluster, MultiFunktionCamera, ESP and SGR).

Anything i can do to check about the command internal loose pins?
:
Maybe i can open and resolder?

CaliBenzDriver

Congratulations, you've just saved your familly a big stack of Euros to spend on tapas this summer.

How did I know... It's a Mercedes, engineered to be predictable.


For your CAN issues, lets start now with a clean-slate:
-- Reset all faults then rescan to get an updated list of all faulted modules.
-- From there we'll try to prioritize as sometimes one bug triggers another one: nested faults.

Let's see what is up now with your CAN chaos.

Make sure you never drain BATT while scanning either plugin charger or idle your engine.