Hello,

I got a CEL in the car after driving about a mile after a really cold start. It was P0400 code (Exaust Gas Recirc Flow Malfuntion). I hit the reset on the dash. The next day the CEL went off also. Will the CEL comback on if it is still a problem or will I have to erase the code first?

What are the typical problems associated with a P0400 code?

Thanks,
Jay

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1998 E300 Turbodiesel 190,000 Elsbett Conversion
(Sold) 1992 300D over 251,000 Greasecar Conversion
Over 70 K of veggie miles total.
Follow link below to see the conversions and instructions.
http://www.geocities.com/jaycimini/MainNavigationPage.html

Just before I bought my car, on a test drive, I got a cell. Turns out it was EGR related. The cell would go on and off, based on the driving cycle. If I drove it easy, then the light would go off. But the car didn't quite drive right.

Do you still have good turbo boost? That was one of the symptoms, when I was on my test drive. Dip into the throttle, and the CEL would come back on. After about three drive cycles, the light would go off.

My bet is, you need to fix something, and it's probably related to vacumn and the EGR. I can't be more specific, because my dealership fixed it before I took delivery. And, they were pretty hush hush about what it was.

99 E300, 72K and counting...

Reset will not clear the CEL.

The code was most likely a one time event and after the 3rd cold start it cleared itself when the fault had not re-occured during that time.

If the fault occurs again the CEL will report it.

I've not expirienced PO400 before, I suspect it has to do with the waste gate. May have been slugglish to open or close in the cold causing the fault?

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Both the EGR and the Turbo Wastegate have vacuum solenoids that I have discovered don't like the cold very much. Chances are you will get the CEL light back on at some point, it's usually an early sign of a failing solenoid but could also be a clogged filter on the bleed line from the solenoid.

The solenoids are identical and if the CEL comes back you can swap them between the EGR to the Turbo Wastegate to see if the fault code changes, then you will know for sure. You will get a different code for the Wastegate solenoid...IIRC it is P0243 but it is definitely different than the EGR one.

You can find the solenoids by tracing the vacuum hoses off the Wastegate and off the EGR back to little black boxes with an electrical connector and 3 hoses to each one. One hose goes to the vacuum source, one goes to the thing being controlled and one goes to the little "bleed filter". Sometimes the little filter gets clogged...if the codes don't change after swapping the solenoids check the filter on the EGR side and replace it if it looks like it could be plugged in any way, it's a cheapo part.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz