Hello to all Sprinter 906 experienced,After spending >500€ and a few hours unsuccessfully on the problem "AdBlue fill level remains at 1/4 - refill AdBlue" I am now asking here for empirical values.- AdBlue light stays on- AdBlue filling level remains at 1/4 even when the AdBlue tank is full to the brim- The message Refill Adblue appears again after each startIt's about a 2014 319CDI Sprinter Mixto.- Visual inspection for marten bites (free commercial vehicle workshop)- Exchanged the BOSCH AdBlue pump (which is in the bottom of the tank) for a €400 new part because the workshop thought that the ultrasonic level sensor was part of the pump and could be the cause of the errorOf course the error is still there.Does anyone have any tips or ideas for further troubleshooting?Get an answer within 90 minutes from Europe's largest car and motor community with over 50 million posts.