As cars have become more complex, the number of different dashboad warning lights has grown significantly. Modern electronic systems like airbags or stability control are constantly self-testing and it's important for you to know whether a warning light requires immediate attention or whether you can continue your journey and get a garage to investigate later. If a warning light comes on (or fails to extinguish after you've started the engine) you should stop as soon as possible in a safe place. Many warning lights are specific to the car make or even the model - the vehicle handbook should give you a detailed explanation of their meaning and the action to take.
20th Jan 2015