2.3 1 stands for ground wire, that is, ground wire.
3.x is the live wire controlled by the ignition switch and passing through the unloading relay, usually a high-power electrical appliance, that is, IG electricity. Such as wipers, heaters, air conditioners and other equipment.
4. 15 and x are the live wires of the ignition switch, which are usually on.
Extended data:
Automobile circuit diagram is divided into external circuit part, internal connection part, component part, relay/fuse and its connection part.
The outer lines are drawn with thick solid lines in the circuit diagram and concentrated in the middle part of the circuit diagram. Each line is marked with the color and diameter of the wire. Line segments have terminal numbers or socket numbers to indicate their connection.
The internal connection parts are drawn with thin lines on the drawing. This part of the connection exists, but the line is invisible. These lines are marked only to illustrate this connection. It also makes the circuit diagram easier to understand.
Electrical components are the main parts in the circuit diagram, which are represented by block diagrams, supplemented by corresponding symbols in the diagram. Each component has a code name, for example, A stands for battery; V7 stands for radiator fan, etc. The connection points of electrical components are marked with labels, which can be found on the components. For example, the starter B has two nodes, reference numeral 30 and reference numeral 50.