laguna 3 engine failure warning

ive had my laguna 3 1.5dci for 3 months with no problems and on saturday i was driving down the road when the engine failure warning came on. nothing sounded different, i dropped it into the dealership today they havent phoned me back. its still under warranty so im not worried about the cost, but i am worried they might fob me off so i was wondering if anyone had any suggestions as to what is wrong? im only getting 33mpg also i think this is low but the dealership says its normal enough.

thanks.

laguna 3 engine failure warning