ADBLUE IN YOUR ELECTRICAL PLUG? LOSS OF PRESSURE FAULTS? 
You're going to need a seal kit! Once this fails the adblue pump is leaking urea into the adblue module destroying every component inside! I'd be looking at changing the internal track if it's contaminated or corroded and the adblue pump too!
This seal kit includes the troublesome valve membrane which sits behind the Adblue pump which will fail as I've shown on my video strip downs.
Also included are new seals for the 4/2 reverter valve which changes AdBlue flow in the adblue pump so within an hour or two you can get your pump working and back to factory pressure in no time