This may have been covered here before,but I thought I would post my recent experience with my 2005 petrol focus.About three months ago the instrument panel began to play up .the whole display would go out for a few seconds immediately after starting. The immobiliser light would continue to flash occasionally and sometimes the engine systems light would come on. It turns out that these were all early signs of a dying battery , although it has taken three months for it to fail to start the car.Apparently the cranking voltage becomes so low that it upsets the electronics momentarily ,when the alternator kicks in all returns to normal. A new battery has removed the symptons ,the one and only time it wouldn;t start was right outside my local Ford dealer.