I bought a Mercedes Benz C220CDI in December 2010 from Mercedes-Benz Bridgend in Wales. So far I've done about 4,600 miles but I have an irritating fault. The engine management warning light came on about month ago. I phoned the Mercedes emergency line to be told if the light was yellow I could drive the car and to contact a dealer. I phoned the dealer and booked it in. By the time I got there the light had gone out (after 3 days on).

I was told a sensor needed to be replaced and it would be ordered. Later, I took the car in to have the sensor changed and I was told it was the sensor for the diesel particulate filter. All was well until yesterday when I got in the car and that darn light was on again. That's now 3 times that light has come on and twice it's gone off of it's own accord.

The only similarities I can find between the emergence of the light is that I've done some short trips with a number of stops just prior to the light coming on. But the car has done quite a lot miles since I bought it, so it's not that I don't drive it on the M-way. It's a low revving engine so at 70 mph it's doing less than 2,000 rpm in 6th gear (my car is a manual). I have put in diesel from an ASDA supermarket and don't know if that's the reason.