S320 W221 exhaust back pressure sensor

Kay187

Member
Joined
Aug 31, 2012
Messages
55
Location
Scotland
Car
S-class 320 CDI
Hey guys,

Need some advice - what should the normal values be for the back pressure sensor? I have a S320 cdi w221 model with 137k miles on it.

Mines are 970mbar when off
Around 2400mbar when idle
About 1200-1500mbar when reving around 3k.

Do these figures look normal?

Symptoms of car - it's kangarooing with power and I lose kickdown intermittently. Sometimes car runs fine with good power and other times it hesitates to pull like there is a blockage somewhere.

History
I've been to a local mechanic as well as an indy who kept getting different codes repeatedly.

Local mechanic cleaned egr but advised no real fault seen with it. Symptoms were bit better but progressively got worse.

Indy tested turbo and inlet shutoff motor amongst few others on star and advised turbo actuator faulty. This was replaced with refurbished one which slightly improved intermittency of symptoms but fault still there with different codes pointing to egr valve. This then replaced with a brand new one and codes cleared for a little while but eventually egr valve code came up again. Incidentally all exhaust smoked cleared as sometimes I'd get white smoke from exhausts.

Dpf not clogged and regens ok. I have a mb carsoft and have confirmed this with the readings I've got on different occasions.

I've looked around forums for possible fixes and the exhaust back pressure sensor seems to be a possible culprit hence the question.

I hope someone can help as I've spent quite a lot of money on the car and it still not fixed which getting very frustrating

Many thanks!
 

OneForTheRoad

MB Enthusiast
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Apr 20, 2015
Messages
2,730
Location
uk.
Car
2017 e350 c207 .. +65 ford kuga 2.0 cdi zetec awd..
950 to 1050 at idle. I ran my engine with it removed and still saw stupid readings. There is supposedly a pin hole in the top that gets blocked. I renewed the sensor anyways and it cured my engine. £47 @ mb.
 
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Kay187

Member
Joined
Aug 31, 2012
Messages
55
Location
Scotland
Car
S-class 320 CDI
950 to 1050 at idle. I ran my engine with it removed and still saw stupid readings. There is supposedly a pin hole in the top that gets blocked. I renewed the sensor anyways and it cured my engine. £47 @ mb.
Thanks for confirming the idle readings, that definitely helps :) With the sensor disconnected I was getting around 4500mbar???

I'll have a look at the said pin hole but for the minor cost I'll just replace it to eliminate. What kind of issues were you having with your car?
 

OneForTheRoad

MB Enthusiast
Joined
Apr 20, 2015
Messages
2,730
Location
uk.
Car
2017 e350 c207 .. +65 ford kuga 2.0 cdi zetec awd..
Wont rev beyond 3k . Very lumpy. Limp mode no boost . Gearbox erratic.

Id say yours is toast if its giving readings disconnected.
 
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Kay187

Member
Joined
Aug 31, 2012
Messages
55
Location
Scotland
Car
S-class 320 CDI
Wont rev beyond 3k . Very lumpy. Limp mode no boost . Gearbox erratic.

Id say yours is toast if its giving readings disconnected.
Yep pretty much same as mines then!

I don't suppose you have a part number for it?
 

OneForTheRoad

MB Enthusiast
Joined
Apr 20, 2015
Messages
2,730
Location
uk.
Car
2017 e350 c207 .. +65 ford kuga 2.0 cdi zetec awd..
Ring a dealer cos the numbers change all the time as parts are updated.
 

OneForTheRoad

MB Enthusiast
Joined
Apr 20, 2015
Messages
2,730
Location
uk.
Car
2017 e350 c207 .. +65 ford kuga 2.0 cdi zetec awd..
Ok will do. Many thanks for all your help, top man :)

Will update post once fitted.
Watch for the metal washer on removal.
 

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