There's a rather loud buzzing noise coming from the engine. Today's the only day I have ever heard it, it just randomly started happening. It starts as soon as I turn the ignition on, and it stays on. But I'm not sure if the engine management light is supposed to stay on after the coil icon disappears. Anyways, when I start the engine and go for a drive, the sound is still there and after I switch off the engine, the buzzing sound continues for about 20 seconds or so and then switchs off. So I'm a bit worried!