My 2011 E350 Bluetec has 31,822 miles and the check engine light came on. The dealer performed a major service at 28,000 three months ago and today confirmed the Adblue sensor was failing, $1900 to repair it. I saw the AdBlue kit and it is extremely poor engineering to require the entire Adblue system to be replaced for a failing sensor. I drive very low miles each year and expected this car to have 100,000 plus miles before any major issues arose based on the marketing hype MB put out with its BlueTec designs. My concerns at purchase were addressed with "MB does not put out a questionably designed product". Well, what relief is there for a car with this problem and so few miles? The AdBlue was added twice since new. What is the failure rate for this part? It will help me determine whether to keep this otherwise beautiful car.