Hi All

UK member here with a 2011 W212 saloon/sedan E250 Diesel, full Mercedes history so serviced as per schedule etc.
While driving home I noticed that my engine was revving much higher then usual before upshifting, it was revving to 2.5k or a bit higher before shifting in eco mode, it was like this all the way home, about 40min journey.

The next day the EML light also came on, called Mobilo who found 2 faults logged:
1) P023714 - the boost pressure sensor has a short circuit to ground - this is what had triggered the EML.
2) "mil off. manifold flap dtcs also present" - it was relating to manifold actuating flap, he said this one may be being caused by the faulty sensor above however so he said first point of call was to replace the sensor.

He replaced the boost pressure sensor (5 min job) and just took 1 test drive and left, when I then drove the car the EML light was back, took it into a independent specialist with STAR and they found the same faults logged.

Indy said it sounds like they replaced the wrong boost pressure sensor, the tech had replaced a sensor in the middle top of the engine bay which was easily accessible, apparently theres another one towards the lower right of the car that needs replacing, when I spoke to another Mercedes tech however he advised theres only one in the car..

Any ideas on how many sensors this car has? they want to replace the 2nd one, if that still doesn't fix then they've advised a new manifold which is very expensive.

Advice appreciated as getting conflicted info and am very confused

I can provide part numbers of the old and new sensor if that helps as I kept the old part and the new box, the part numbers are diff between old/new.

A LOT.
I count 7 sensors on exhaust alone and I too replaced wrong Ox sensor before dealer told me the other, identical sensor is bad.
Dealer wanted $1000 + for the job ($660 for sensor), but I bought the sensor for $350 from internet dealer .
Unfortunately the system is still relatively new and DIY don't really exist , so IMHO having them replacing 2nd sensor is your only quick option.
But dealer with SD should be able to diagnose the problem before sinking money in it. If not - I would say they don't deserve the troubleshooting charges.
Manifold is probably having sot build up. I just cleaned manifold flaps on 624 engine. Not hard job on its own, but getting manifold out takes time.
Than US dealers "don't do cleaning" and they do replacement only. Are UK dealers the same?
Good luck.
Posting it in diesel section would give it better exposure.

Apologies I meant any idea specifically how many boost pressure sensors the car has, as if it does have 2 then the wrong one was replaced, at the moment i've got 2 mechanics telling me diff things (1 says 1 sensor other reckons their are 2), I'll try posting in Diesel too

You need to find a mechanic not only with proper scanner, but also a knowledge how to use it.
Not an easy task.