Many cars, especially more modern cars have a number of different lights on the dashboard which illuminate when there is a problem. It may be that you are unaware that there is an issue with anything until you are driving along and a warning light comes on or the car won’t start but something is lit up on the dash.
Cars are often subject to break downs and mechanical failures some of which we are not warned about and will happen for no apparent reason out of the blue. Other problems develop over time and we may have had warnings about them which we have ignored. Any warning light that appears on your vehicle should be checked out. Sometimes the fault is not actually with the part that the warning system is set up to advise you of. It may be a fault with the sensor for the warning which still needs to be investigated anyway. Sometimes, more serious problems will cause your car to go into what’s known as limp mode. When in limp mode, the car is limited to the speed it can do (often to around 20-30mph). Hooking a car up to a diagnostics machine will help to identify if there is a fault and where the issue is, making it a lot easier to fix. Usually once the fault is fixed the car will automatically go out of limp mode.