C350 EGR Value Issue?

[Reddy]

Hi,

Over the last few weeks I have started having problems again with my 2011 C350 CDi Auto (W204). It is running poorly - higher revs before gear changes, unsteady engine revs around 1200-1500 rpm, lack of power. I now have a EML on and my cheap obd reader is reporting P0404 and P0405 codes.

I thought I would start with the EGR valve since both these codes relate to this. I removed it and although it wasn't as dirty and clogged as I expected (and hoped), I cleaned it, checked the arm was free and opened and closed the valve as expected. I couldn't check the electrical side of it as I didn't have the tools or wiring diagrams.

I replaced the valve in the car, hopeful it had cured the problem. Initially, all seemed ok until the engine got up to temperature, then the issues returned, along with the P0404 and P0405 codes.

My next step is to replace the EGR valve, but I have read online that people suggest unplugging the EGR valve entirely and seeing how the engine runs. I did this, but the performance did not improve and the codes (plus some additional ones) were still being triggered. Before I spend the £££s to replace the valve - could this indicate the EGR valve may not in fact be the issue after all and the fault could be elsewhere?

Any help or advice would be greatly appreciated.

thanks
David

 

[McDonald]

The standard advice is, get it on Star before guessing which parts to replace. Definitive readings are the way forward.

 

[Wighty]

As above , an MB specific code reader like STAR (at an Indy) or icarsoft readers is the way forward . You can’t replace the egr at over £200 ? On a hunch , based on a genetic code reader
Unplugging the egr will always throw up fault codes .
Where do you live so someone can recommend an Indy ?

 

[Reddy]

Thanks.

I did take the car to an indie about 8/9 months ago when I was having similar issues and had a P0401 code. At the time I paid for a diagnostics on star but they weren't entirely certain what was causing the issue. They suggested that a software upgrade may fix it, but if this didn't work the next step would be to replace the EGR valve. The software upgrade seemed to work (for 8 months or so), that is until now. Bearing in mind their advice at the time was to replace the EGR valve if the software upgrade hadn't work, that leads me to think that they will recommend the next step is to replace the egr valve anyway.

I have found a second hand egr valve for about £120 which has been tested as fully working, so my dilemma is whether to spend around £70? for another star diagnostics when it's entirely possible (likely?) they will recommend egr valve replacement anyway, or put this cost towards getting the 2nd hand valve and at least rule that out one way or another?

thanks
David