W204 in limp mode.

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Hampstead

Member
Joined
May 23, 2020
Messages
31
Location
Essex
Car
C350 CDI W204 2010
I took my car for diagnosis and the error code pointed to the EGR valve.

They fitted a new one and it went into limp mode on the way home. They have tried various things including new hoses and replacing the engine exhaust temperature sensor.

So, today I bought an ODB reader and the code was P0401 Exhaust EGR Flow Insufficient.

It’s a W204 350 CDI 2010.

Any ideas what they have missed!
 
The generic OBDII reader won't give you much info.

If you intend to tackle this DIY, then at the very least you'll need something like the iCarsoft MB v2.

Better still, take it to a specialist who will have proper STAR diagnostic computer, and more-importantly understands how to view live data and how to carry out the diagnostic process.
 
I’m taking the car back to them after the weekend. I was hoping there would be a simple thing that commonly gets missed.
 
This sounds like a typical boost/MAF/DPFE problem which is very common to kick up a FALSE P0401 including on any STAR diagnostic hence the reason why they have replaced the EGR when its clearly nothing to do with the EGR valve.
 
This sounds like a typical boost/MAF/DPFE problem which is very common to kick up a FALSE P0401 including on any STAR diagnostic hence the reason why they have replaced the EGR when its clearly nothing to do with the EGR valve.
J
 
This sounds like a typical boost/MAF/DPFE problem which is very common to kick up a FALSE P0401 including on any STAR diagnostic hence the reason why they have replaced the EGR when its clearly nothing to do with the EGR valve.
So, what’s the next step? The garage have given up.
 
Have a look for any carbon blockages .pre and post egr. Also did the new egr come with exhaust back pressure sensor or did they use the old one ?
 
Can u stick a picture of your engine in here for me to see please. Carbon blockages etc and sticking EGR valve and pipes n stuff are all never the source of this problem and this is why it is so frustrating for customer and the garages. The garages follow protocol. Change part according to fault code. Unfgortunately 9/10 the P0401 is never the EGR valve. A picture of ur engine please if possible or stick ur VIN here and i can get a proper look at it and others can maybe help more with the VIN being able to access what it has and does not have.
 
Model: C Class (2007-11)

Range: C350 4Dr Saloon 3.0 CDI BlueEfficiency DPF 231 EU5 Sport Auto7

VIN: WDD2040252A377413
 
Well there are some good indy's in Essex I use one in Colchester,there is a couple in the Romford and Basildon areas,you need it on a star.
 
Was looking at ur engines basics. From memory I have had a faulty MAF sensor kick up an EGR P0401 fault before on one of them. I would attempt to do this. UNPLUG THE MAF sensor. Tuck the connector away somewhere safe and close your bonnet. Then clear the codes. then drive it and see if it still goes into limp mode. This needs to be done.
 
No. You have got 2 sensors. 4 wire sensors plugged into each side of the airboxes. 1 on the left us under the word bosch. When they are unplugged. Run a scan and delete codes. The engine light will come on. Ignore it. Also another 2/3 codes aswell. Ignore them. 113 and 102 .... something like that. Make sure AFTER you have unplugged both MAFs you delete codes then run the car fir a day like that. Deleting the codes every so often thruout the day. See how it runs like that n report back.
 
No. You have got 2 sensors. 4 wire sensors plugged into each side of the airboxes. 1 on the left us under the word bosch. When they are unplugged. Run a scan and delete codes. The engine light will come on. Ignore it. Also another 2/3 codes aswell. Ignore them. 113 and 102 .... something like that. Make sure AFTER you have unplugged both MAFs you delete codes then run the car fir a day like that. Deleting the codes every so often thruout the day. See how it runs like that n report back.
Will do, thanks.
 

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