A truck owner reads a wiring diagram by identifying the connection between the symbols found in the diagram and the actual elements of the trucks electrical system. Truck wiring diagrams typically also include a key that shows which wires connect to the different internal components, such as a stereo.
It is important that the truck owner makes sure she is looking at the wiring diagram for her exact make, model and year of truck to avoid making decisions based on incorrect information. Even if the diagram is for the same make and model of truck, if it is for a different year there is no guarantee that the wiring is the same. Acting based on the wrong diagram may lead to damaging the truck's systems or the owner herself.
Once the owner verifies that she has the correct diagram, she needs to identify the component that requires the work. For example, if she needs to repair the wiring for the truck's air conditioning system, she should check the diagram key for the location of the air conditioning wiring. She then needs to look at the symbols on the diagram to locate the proper circuits, wires and diodes that control the system to make the appropriate modifications or repairs.