I have the engine management light on all the time on my 2013 C180 Blue Efficiency. I ran a diagnostic on it and it came up with a PO128 fault; Coolant thermostat, Coolant temperature below thermostat regulating temperature. I assumed this was a sticking thermostat. As the car was bought last July and has a Mercedes used car warranty I left it into my local dealership today to have it fixed. When I went back to collect it I was told that the problem was actually the engine heater element which wasn't reaching temperature fast enough. I told him that it wasn't reaching temperature at all as on the 25 mile drive to the dealership it hovered between 60 and 70 degrees. Anyway I was told that they didn't have the necessary parts, this engine element and also some seals and that they would have to check if the work was covered under my used car warranty. Anyone know what this engine heater element is and if it is covered under the used car warranty as I'm a bit concerned that they are simply looking for something that I can be charged for! Also am I doing any damage to my engine by driving it with this light on? I was told, 'probably not!' My used car warranty is prefixed with the letters T1MB which I'm assuming stands for Tier one which is I believe the highest level of cover. The car has only 30,000 miles from new so is well under the 100,000.