If this fault comes back on just with switching on the ignition then you have a problem with the EGR being stuck open/closed .try another EGR valve , but first check the wiring harness for any shorts to ground ..as a short will also give you this code .
Wiring harness good replace the EGR valve .
Still need additional information then please get back to me with the reply button, and not the poor or bad service, this way i can get back to you or suggest another expert if needed.Your deposit does not pay me until the answer is rated in a positive way,A bad rating does not constitute a refund.If you are not happy or you have sorted out your problem before the answer then please let me know with the reply button .Kind regards Greg.
Soot in the coolant water .is a sign of a headgasket issue .
Do a Co2 test to confirm a bad head gasket .
Then please get back to me .