Whenever a bundle of wires passes through or attaches to a component of the car that might have to be removed, there must be a connector to allow for that removal. A single connector can have more than 100 wires. The connector on the engine control unit has more than 100 wires. In the past, unreliable connectors have been the source of many electrical problems. Connectors have to be waterproof, corrosion proof and provide good electrical contact for the life of the vehicle.
Modern connectors have several seals to keep out moisture.
The parts of a typical automotive connector. Everything on the left connects to everything on the right. To make this connection, there are a total of 23 separate parts. The main parts are the shell, the pins and sockets, the pin retainer and the seals. The shell is an intricate piece that has a complicated shape.