Have a 2012 E350 Bluetec diesel and got an eng chk lt with a P20BD fault code for Reductant Heater Control. MB dealer says the control that heats exhaust fluid and provides volume info failed and will take $1500-1800 to fix. Since this us part of the exhaust system why us this not covered in 8o k mikes/ 8 yr exhaust system warranty?

 

I believe the warranty covers the drivetrain and engine issues only.