Below are general electrical schematic diagrams of the models: BMW 316i Kat., 318i Kat., 318is Kat., 320i Kat., 324d, 325i Kat, produced since 1990.
Examples of symbols on electrical circuit diagrams
1 Cross section, mm²
2 Main color
3 Additional braid color
4 Terminal number
5 Terminal designation
6 Threaded connection (cable lug)
7 Round connector
8 Flat connector
9 Round connecting pin
10 Flat Connector Pin
11 Soldering point or connector
12 Designation of detachable connection
13 Wires without cross-sectional designation have a cross-section of 0.75 mm²
14. Lead-in element
15 Element present in the diagram
16 Terminal in serial electrical circuit
17 Only for vehicles with manual transmission
1 Cross section, mm²
2 Main color
3 Additional braid color
4 Wire number
5 Terminal designation
6 Terminal connection (the end of the wire is galvanized)
7 Threaded connection (cable lug)
8 Round connector
9 Flat connector
10 Round connecting pin
11 Flat Connecting Pin
12 Element supply
13 Element present in the diagram
14 Mass
15 Soldering point or connector
16 Shielding
[Information taken from this resource «BMWman»]