ok so the engine check light has been on for the last 18 months (we are poor students and struggle to pay for mot tax and insurance instead of services) now i have done some stuff on cars before so want to see how to diagnose the reason for the check engine light how is it done i know that in the states a simple device is bought but can i get the same over here? also when we put our foot down on the motorway or put the engine under stress going up hills there is a rattle mixed with the sound of an exhaust blowing mixed with a vibration noise had the exhaust check and its not this got any ideas?

many thanks
andy