Several electrical accessories in the vehicle, such as the fuel injection system, horns, starter, and fog lamps use relays to transmit the electrical signal to the component. Relays use a low-current circuit (the control circuit) to open and close a high-current circuit (the power circuit). If the relay is defective, that component will not operate properly. Relays are mounted in the engine compartment fuse/relay box. Relays can be found in other locations; check your wiring diagram and component locator for exact locations. Note: Some relays are energized by a computer using a negative or positive feed. Do NOT bypass a relay from these connections unless you are sure of the source of the signal. The wiring diagram shows the routing and exact location of these input voltages.