The electric systems control every aspect of the car from how the engine works, when the car changes gears, how much fuel the car consumes, to mundane bits like how fast your window winds up and down. Check whether each button in the car works as it should. Make sure also to inspect the vehicle for visible marks around the buttons. Such marks could give away shoddy repairs or abuse of the vehicle. Used cars usually have a plethora of minor electric faults that could frustrate you along the way. When the systems cease to work, for instance, you have to dig into your pocket to pay the repair costs. Another bit of the electric system is located under the hood in a small box known as the ECU (Electric Control Unit). This unit controls the engine, transmission, acceleration, braking, and other crucial aspects. Ask the seller to show you the unit and inspect it for signs of damaged wires around the ECU. Such damage acts as a pointer to the state of the vehicle.