andrewpaul

Exhaust back pressure sensor - purple mark on it
Hi have a few issues with my ML320CDI which I believe are due to the Exhaust Back Pressure Sensor. This is the sensor at the back of the turbo sitting between the turbo and EGR.

​​​​​I did monitor live data from this sensor and it seemed to be working. Any tips on what live values I should be seeing?

​FYI we are in our winter season in New Zealand.

- Car starts in the morning stays at lower than idle revs then cuts out acceleration cuts the engine.
- After a dozen or more starts I may be able to rev the engine and drive
- On driving the car will buck for a while
- All this with no CEL

​​​​​After a while of being started and I presume warmed up all the issues clear up.

I have taken the sensor off and cleaned it with brake cleaner this improved the morning starting but the car still bucks for a while.

If I unplug the sensor the car seems normal starts without an issue and does not buck so have been driving with it unplugged and now have a CEL.

​​Should I try another clean of the sensor or is it a waste of time?

I believe there are a few variants of this sensor. My ML has no DPF and therefore no Exhaust Pressure Sensor (the one with 2 pipes installed in the drive shaft cavity). Any thoughts?

Thanks.

Roy.Pedersen

Did you solve the problem?

andrewpaul

Hi Roy

Yes I did just got a new sensor from Pelican Parts in the US for $40. (I am in New Zealand)
This was not an original MB part but the cheaper equivalent version.
The new sensor transformed my ML.
I believe a lot of people are changing Turbos thinking that they are faulty they should change this sensor first.

Cheers and best of luck.

Roy.Pedersen

Hi,
Thanks for your valuable answer. I got exactly the same problem on mine ML, when the enige is cold I need to disconnect the sensor to get the engine started.
No fault codes on diagnoses or CEL.
New sensor are ordered.

Brg
Roy

flybd5

What reader are you using to look for fault codes? If it's not , you are not really getting anything useful.

Roy.Pedersen

My dealer use Bosch ESI (Tronic) 2.0, anyhow I will have a STAR diagnoses done this week.

Roy.Pedersen

What type of scanner do you recommend to use for MB, except of STAR.

flybd5

My message above has a link to the Amazon listing of the scanner recommended by the resident guru, Maj. Dundee.

Roy.Pedersen

Hi,
Thanks for info, I will consider to get one.

I tried to start the engine again this morning with same result, runs for 5 sec and then stop, and then the CEL came up. (Code 0472).
Changed the sensor with a new one and cleared the code, now the engine start and runs like it should.

Thanks for assistanse.

andrewpaul

I have an Autel MD808P Maxidiag Scanner that scans all the W164 modules and resets fault codes.
Has a range of car manufacturers US/Euro/Asian on its MicroSD card. Car model data gets updated on their website and can be downloaded to the unit.
Cost $240 and works really well. Great piece of universal diagnostic kit to own.

DereckHelga

Hi Everyone ,
The simple truth is that when this sensor goes all that can be done is a replacement , cleaning of fixing wont help.
It is also not something you can maintain or service , if it goes , it goes ,no matter where you are and it is the "no matter where you are " that greatly concerns me about MB , the tech and the integrity of the car.
If you're in town or close to one it is a no-brainer ,
Again , what if you're not .
Is the answer not maybe to replace at specific intervals , like cam belts , preventative maintenance style , to the likes of aircraft maintenance ,
The car is completely useless if this sensor goes and what is even more scary is that turbo's are being replaced when this cheap little sensors goes , I note someone else has also mentioned this .
Any of the readers can pick it up if the mechanic or technician knows his way around , MB's diagnostics I am told are way better than other German brands.
If for some reason you are told to replace a turbo , have this checked 1st .

Hope this saves someone a lot of money and agony somewhere.
Dereck

DereckHelga

Hi Roy ,
I think we should carrying an extra 1 when going on trips .
This is a major vulnerability.
Regards
Dereck

Paul Z

My ML 320Cdi 2008 got same issue Andy it bother me a lot. Every morning I start the car, the engine will shut off after 1-2 secs. If I am lucky, I can start to drive it with a really dangerous situation. The SUV just like a jumper car. Oh my GOD. Before notice this form. I spent tons of hours and I did find this ebp sensor cause the issue because once I takenoff the socket. The SUV runs as normal but having CEL p0472.

Yes, it is exactly same as yours.

I bought a benz parts and replaced it today. Hope it fix my SUV too.

Will keep an eye on it.

Thanks for the info sharing. And hope this help others.

The only thing I knew which might related is the issue began after I cleaned my MAF and MAP. That does not make any sense why the ebp got problem after then.



Ebp

Maj. Dundee

You need a scanner to check for codes.

Roy.Pedersen

Don`t waste your time to clean the sensor, change it.

Paul Z

The sensor replacement actually got the best result, My ML 320 works as normal. Thanks all.