The engine management warning light on my wife's 1.4 Focus flickered on the other day when driving. It did if for about half a mile, then went out. It did it again when she started it this morning. It flickered for about 3 seconds and went out and hasn't come on since.

Are their any likely culprits to check before I give Ford far too much money to plug in their diagnostic electrictrickery - The car drives faultlessly otherwise.