Lighting and Comfort
Interior and Exterior lighting can fail or become faulty, Air Conditioning and Pollen Filters can cause a number of issues, Electronic seating can suddenly break, as can electronic boot switches and other internal devices, all of which will be reported as a fault by your vehicles ECU.
If the lighting of your Vehicle is at fault it not pass it's MOT and will not be legal on a UK Road. You could alos be stopped by an officer of the law and fines imposed should your lighting be deemed of a sub standard.
Safety & Tyre Pressures
All modern vehicles are equipped with Air bags that in the same way as other components can fail or become faulty. Many of the newer, more modern vehicles are equipped with Electronic Parking Brakes that can render a vehicle useless if they are reported by the ECU as faulty. Some modern vehicles are also equipped with Tyre pressure sensors that can report that tyres are inflated correctly when actually they are not, placing the occupants at risk.