BullDozer

Hi folks,

I have a 2012 ML350 W166 with the OM642 diesel engine. I have been experiencing some EGR issues recently, with the engine light popping up at coolant temps around 80 degrees. The engine light typically shows up during long trips where the engine is at a constantly high temperature. It only shows 3 specific codes, either at once or sometimes one at a time (as per the image below).

Fault codes on Xentry

• 14B100 Component ‘Hot film mass air flow sensor’ has a plausibility error
• 156000 The negative control deviation during exhaust gas recirculation control is too high
• 111800 The upper limit value of component ‘NOx sensor downstream of SCR catalytic converter’ has been exceeded

I never get an engine light popping up on short trips, but this is probably because the coolant temps only reach a max of around 65 degrees. Using Xentry, I tested the EGR system where it changes the ‘on/off ratio of exhaust gas recirculation’ and measures the air mass flow. I conducted two tests at two different temperatures: 73.7 °C and 77.6 °C. The results are shown as follows.

Xentry EGR test @ 73.7 °C
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Xentry EGR test @ 77.6 °C

The air mass values are below the lower limits in both tests, as shown in the graphs. It seems like as the coolant temp rises, the less air that flows into the engine as the EGR valve is not opening/closing correctly, therefore throwing up the error codes as mentioned above as they all seem to be linked. At 95% actuation, the air mass value appears to be okay, and within range, so I am thinking there’s a slight chance it’s a faulty EGR actuator (Y27/9), albeit I have done a manual test via Xentry, and it seems to be working fine as per the test.

What I have done:

• Cleaned the two mass airflow sensors with ‘CRC mass airflow sensor spray cleaner’
• Replaced seals on turbo inlet, air filters, intake mixing chamber and EGR bypass flap unit
• Removed and inspected the EGR actuator valve. Moves up and down fine, lubricated the linkages. Replaced the gasket when reinstalling
• Tested the ‘Y27/9 Exhaust gas recirculation actuator’ via Xentry. Opening it and closing it as per the test and it all works as normal. Open -> air mass falls, close -> air mass rises (Or vice versa, I cannot remember)

My next step for maintenance purposes and the fact that I had to replace a leaking water pump is to replace the thermostat. I also noticed recently that the engine takes an unusually long while to warm up (winter season). Any help on this issue would be much appreciated.

Cheers

BullDozer

Any ideas or hints folks? Thermostat is still on the way from ECS Tuning because Australian prices are ridiculous.

NNNN

Have you tried to clean EGR valve?

BullDozer

Do you mean the EGR flap at the front of the engine part of the 'air mixing chamber'? If so I have cleaned that.

Mijanboy

is DPF in the car?

BullDozer

Yep. Has also recently been cleaned.

Mijanboy

If I think logically, everything is Okay when the car is cold. Only when it warms up do problems begin. Only one of the 3 problematic devices does not work cold, but starts working when the engine warms up = EGR valve. I would focus my attention there.

BullDozer

From my brief testing, the EGR valve seems fine as I have actuated it when warm via Xentry and have confirmed the linkages work on the valve and then lubricated it. If replacing the faulty thermostat doesn't solve it I will definitely turn my attention to the EGR valve again. Thanks

Mijanboy

That's right, wait for the thermostat, because I think due to the low temperature of the engine DPF regeneration does not work and will not work even manually when the car is stopped. Once you've cleaned the DPF, you need to "learn DPF " with Xentry.
If the thermostat does not solve this, I would take the driver and sit down with him with Xentry and monitor the actual values. If there are multiple errors, Xentry has "phenomenon data" next to "error codes" and you can find out details about when the error occurred / at what speed or rpm, etc. /. Borrow from a MAF friend who works 100% in friend car = this will give you 100% confidence that the MAF is OK. The MAF, which is always green in diag but not working properly at higher speeds and is no DTC, is nothing special. Remember that EGR only works when the engine is warmed up to 50 +° C . and it also doesn't work at full throttle - it may come in handy when testing. Write where the problem was. I wish you a quick fix.

BullDozer

Sorry just to clarify the DPF was cleaned many months ago and a DPF 'reset' was performed after fitting it via Xentry. Thanks for the info about when the EGR operates. The car struggles to reach normal operating temperatures especially during winter, so that may be the reason for this issue and I'm really hoping that replacement the thermostat will solve it.

I also hope it isn't a faulty MAF because as you said, I have not found any DTCs regarding the MAF sensors. It is very expensive to replace especially here in Australia and same with the EGR valve! I appreciate the advice Mijanboy

Mijanboy

Hi, I know you wrote that DPF was cleaned up, but you didn't write when and I don't know how many kilometers or miles you drove. Automatic regeneration can start just 400 km from cleaning, but also up to 1200 km. It depends on many factors how quickly the DPF will need automatic regeneration. You made me laugh today. I have a computer connected via TV, so I have a big picture. I looked at your DTC and found out that there is another DTC, you fixed it nicely and quickly ... with a marker
I probably won't please you much now: Look at the first DTC: the hot movie Mass Air Flow ... that's why I wrote you to borrow MAF from a friend.
What mistake did you keep secret from? How much do MAFs and EGRs cost in Australia? Send me the VIN of your car. Good night.

BullDozer

Hahayes I did blank that code out because I was doing some testing with the engine on with the coolant switchover valve and left it disconnected which gave an 'open circuit' DTC. It wasn't relevant so I marked it out and cleared everything after taking the picture.

Yes I believe that the MAF is receiving an incorrect air flow (implausible) that is out of the normal range due to the issue with the EGR system. I tested the MAF sensors in Xentry and it passed fine. All the 3 DTCs are related to each other. Unfortunately I do not have access to another MAF.

MAF (A6420901642) is 983.86 USD (~21,427.59 Kč) delivered and the EGR valve (A6421402160) is 455.18 USD (~9,913.41 Kč) delivered. Both from Latvia on eBay

Mijanboy

These are not nice prices at all ... I will probably sell my w164 when I see it Luckily, the Czechia is a small poor country, so here we have prices a little different ... because otherwise no one would ever buy any part.
Look at us ... at the poor ...


That's about $ 275 for the EGR and $ 415 for the MAF. I don't know how much is the postage to Australia. To get the postman on horseback there at all and bring it to you Tomorrow I can ask him if he goes around ... he carries mail once a week ... if it's not hot or cold, or it's not raining, or if he's not in the mood ...
People prefer to buy used things here. The MAF used will cost a maximum of $ 200.
The problem will be postage ... it will be terrible nonsense. On the other hand, when I shop in China, sometimes I have even without postage ... So it would be necessary to find out what a scam needs to be done , Because giving more for postage than for a used MAF, I would probably pass out..

BullDozer

Just an update on this. New thermostat came, took the old one out to find there was a gap between the rubber seal and the thermostat housing so it would seem that coolant was indeed constantly flowing into the block even when cold which explains how slow the engine was getting to operating temperature. New thermostat had a steel seal instead of the old one with rubber, must've been a new iteration.

Replacing the thermostat only highlighted the EGR issue more as the engine warmed up quicker causing the engine light to pop up once again with the same issues. I've decided just to bite the bullet and buy a new EGR valve as well as a exhaust pressure sensor which sits right next to the valve. Figured it beats taking it to a dealer or Mercedes specialist tech which is my last resort. Mercedes dealers here want over 1000 AUD for the valve, managed to get it from Latvia on eBay for 580 AUD shipped including taxes. Fingers crossed this is what it'll need to fix it!!!!

BrZu

Hello Bulldozer,

I'm from UK and i have a Mercedes Benz S CLASS S350 CDI BLUETEC (ad blue system) and i have the exact same problem like your having with your M class, (we have the same engine) i'm getting the 156000 error code. ,i've changed what you changed and still does the same,
i changed the egr valve with a new one, i've been to a mercedes specialist who tried to help me but he couldnt find whats the fault.

i must mention that my car as well as yours it gets to the right temperature later then usual and the heating inside take more time to get you warm.

Can you please tell me if you fix your car and how did you do it ?

Thank you
Chris

Rameez

My issue was the same and i had a leak form the hose pipe connection from the resonator toward the intercooler!
more over the resonator attachment and it's body o rings and seals had also failed to! It was leaking air from there too!
My friend who is an indi opened the resonator cleaned and and bonded wid a bond back again as parts are really expensive and tough to find in India!
He cleaned the Egr mixture valve it's flaps as well as it's steel pipes and also the exhaust back pressure sensor for the same issue!
Egr vale as a whole was cleaned a while ago!
Drove 150 kms after that on highway speeds and also on loads and no fault coad as of now! Fingers crossed!

BullDozer

Overdue update. All issues were finally fixed in March this year:

14B100 Component ‘Hot film mass air flow sensor’ has a plausibility error
156000 The negative control deviation during exhaust gas recirculation control is too high
These two codes were eliminated through replacing the Exhaust Pressure Sensor (B60) with a brand new genuine Mercedes one. I initially used a aftermarket Febi branded sensor but that didn't work. Performing the EGR air mass as per my original post, it now passes fine.
Note: I also replaced the EGR Valve but that didn't solve the issue so I now have two working EGR Valves...

111800 The upper limit value of component ‘NOx sensor downstream of SCR catalytic converter’ has been exceeded
For this, I replaced the NOx sensor with a used one. This was also the newer iteration sensor as the original one that was in it has been superseded. After replacing, I reset the 'learned' sensor values via Xentry.

Took a long time to finally diagnose and solve the issues, but I'm glad its finally over.