Here we are only 5 months after the DEF tank heater was replaced. Once again this Bluetec is showing it's own frustrations with all the emission B.S. that is choking the vehicle from it's true potential. This time it's the upstream and downstream NOX sensors. Quoted at a little over $1,300 to replace both.....add a little for diagnostic charges and other things that usually you'll have to get done. MB Tech did tell me that at 38,000 miles one of these sensors was replace under warranty, and now again at 82,000 for both. I'll update this once i hear back from MB USA about any financial help they may offer me. I'm really dissatisfied with the cost of repair JUST for the emissions of this 4-5 year old diesel. I'm definitely regretting buying this diesel, maybe i should've went for an ML550 instead, heck even the price of diesel in California is over $4 a gallon so what's the point? As a matter of fact if some Mercedes Benz officials are reviewing my 2 complaints I have 2 options for you guys. Buy my car out for what i paid for it only 2 years ago. Or, back your product and make some critical changes for the design flaws. So far this year (the last 5 months actually) this vehicle has a total of $4,000 plus just for the emissions system that doesn't even need to be there for the vehicle to operate.