colster

car c4 Picasso year 2007 engine 1.6hdi problem for the last 3 years at least when the car has been driven on a longish journey the engine management light comes on with a warning depollution system faulty message as well, this will remain on for a few journeys then clear until it goes on another longish journey when it may happen again. car has done aprox 70000 miles and is driven on mainly short journeys say 5 miles. Any ideas to what the problem is