ML500K

Symptoms happend about a month ago, when slightly accelerating from 45-65mph the sc would engage for a split second and suddenly cut off. Pressing the pedal to the floor the car would only accelerate ever so slowly. I knew the sc clutch has been disengaged for some reason, and NO CEL light. When i slowed the car down a bit and then hit the pedal again, everything would be back to normal, sc engaging and all, back pushed against seat.

Today I finally got time to check it out and it turned out to be a small problem. STAR gave me a P0108 Error: Manifold Absolute Pressure Circuit High Input.


The part that got replace is designated as B28 in star service manual. EPC has the part no. A 004 153 33 28 . The old part has the same part number, so no updated parts.
Update: There is a new part no. P/N: A 005 153 72 28 Thanks OD!

Attached are the location of the sensor, part no. and some installation pictures. as you can see the sensor is actually located on the "charge air cooler"

Steps to change the boost sensor:

1) remove both air filters
2) remove the throttle body
3) remove the right intake manifold facing engine ( Driver side )

You will be able to use an extension wrench to remove the 2 screws holding the sensor.

After replacing the sensor and buttoning her back up, I took it out for a test drive. So far I cannot reproduce the SC cut out and acceleration is smooth as butter. I will test it out for a few more days and hook it up to STAR to see if there are any other error codes. Will update this post after. So there you have it.

loudandheard

That's good to know, I wonder why it doesn't throw a code.

alkrstev

Thanks for the info. Mine acts like its going to downshift and you hear the sc but then the car jerks and no sc. I hope the symptoms dont come back for you. I am going to probably do this myself too.

ML500K

I'm guessing that the ecu doesn't think its that serious of an issue to make it a CEL. I've had my car modded for over about 2 years now so I was sure it wasn't a tune/modding issue. It just happened suddenly one day and it kept on happening about once a day or whenever i decide to hit it to pass a car, sometimes the sc cuts out sometimes its alright; we all kno how that feels when ur car doesn't perform as expected.

ML500K

I'm glad its ok for now. Hope yours is the same issue. It felt like when i'm on the pedal, i feel a slight jerk for half a second ( sc still engaged ) then all of a sudden it feels like i'm putting the tranny in neutral, rpm going up but the car not accelerating, or rather very very slowly. worse that a NA engine. Seems like the ecu sort of put it in a "limp mode" without the CEL coming on.

Budget Baller

I had a similar issue which turned out to be the Intercooler pump. This is good know however Nice write up.

ML500K

Thanks. I use my iPhone to monitor the IAT so i knew it wasn't the pump failing.

c32AMG-DTM

When the ECU decides to shut off the S/C, you're left with a low-compression 3.2L in a moderately heavy sedan. It's an absolute pig when trying to accellerate in that condition, no doubt... seat of the pants, feels like a car with less than 200 bhp. I don't think it's a "limp mode" per se, just a car designed for F/I with the F/I shut off.

FWIW, I think that P0108 is the code that all of the 185 guys/gals get from time to time. Overboosting the stock MAP sensor capacity. Should be most likely to occur in cooler, drier weather and at lower elevation. I don't think it's harmful or damaging to the car, but you should see about datalogging your car and make sure your AFRs are good even during the most demanding conditions (i.e. WOT, max load through the highest gear you can safely test, probably 3rd).

Wilsophia

What is your IAT and boost value?

I m using iPhone (Rev) and Kiwi to monitor my IAT and it go over 100C, but the SC still function ok. I m guessing my apps detection having problem cause I m using a JB version

OverDrive

Thats very intresting, if you have a look at my thread, there was an updated part number for MAP

https://mbworld.org/forums/c32-amg-c...r-part-ii.html

On the EPC when I looked when doing this project came up with a new p/n along with a few gaskets that were different. I went to the dealer and order the part number that was on the EPC, This is what I got,

P/N: A 005 153 72 28

ML500K

Totally, low compression 3.2L is a real dog!

I did my tuning in the dead of winter here and speeds of up to 150mph using real world data logging ( don't ask me where ) And i send my data back to Jerry to have it retuned. Did this about 3-4 times to get it right.

ML500K

Awesome info, I did a search before doing this but i didn't use "MAP" as a search term, which your detailed post slipped through my fingers. I just called my mechanic and asked him about the new part no. and now he will exchange it. Gonna have it replaced today.

ML500K

This happened at around 10psi and my IAT where about 40C / 104F. When I actually gun it, its ok, its only when pressing half way does this randomly occur.

anasdaouk

hey guys i need advise from you on this issue:
car behaves normally all times until i smash it down full throttle on 2nd 3rd 4th gears it cuts gas totally doesnt accelerate anymore i press the pedal its empty and all i can do is park sbhut down restart and here it gors again...on 1st gear if im not goin sideways seems it doesnt do any problem...nota: car does function perfectly as long as i dont press the pedal fully or do a kickdown i even can go 200km/h without problem...any ideas???????plz help

i guess this exactly what u r talking about the boost sensor...it showe failure symptoms after a harsh driving night goin to speeds above 250 several times...opinions plz, any idea about the cost of this sensor?thnxx

C_DirtyTwo

Sensor is inexpensive around $15 I think. Easy DIY install too, however it could be your Intercooler pump too so I'd look into that first.

anasdaouk

man i changed my ic pump two months ago surely not from it, and from driving experience a failing ic pump will shut down on 160 k or so and will fail on high revs i can go up to 5800 with no problem so thats why i eliminated that option..

ali saklaoui

Hi Anas,get your car and i will see where is the problem,these cars are so simple...

ML500K

After I changed my boost sensor I never had my symptoms anymore.

ML500K

I meant to say intake air temp sensor. I had the boost sensor changes first, cause I says the error in the log, but changing the air intake sensor fixed it for me.