Electrical System

Step by step instructions on how an automotive electrical system works. This article pertains to all vehicles.

Step 1 - The electrical system of any vehicle performs the same function, to deliver and monitor electrical power to various devices and sensors while under control of a computer system.

Main Computer

Step 2 - A wiring harness is used to connect various devices and sensors to either control, or send feedback data to the computer. The harness is also used to control the lighting system such as brake lights.

Wiring Harness

Step 3 - A wiring harness has many connectors that serve as an extension which allows routing to devices which are obscurely located.

Wiring Harness Connector

Step 4 - Connectors are disconnected by depressing a small tab on the side of the connector. Once apart, the male side of the connector is designed with terminals that protrude outward, which fit into sockets on the female side. (Note: Some connectors possess a safety tab which must be removed before the connector can be disassembled.)

Electrical Connector Disassembled

Step 5 - A device connector is used to connect to a particular item such as an ignition coil which is shown here. A safety is used to securely attach the connector to a device, which adds an extra layer of protection from accidental disconnection. This safety clip must be removed before the connector can be released.

Electrical Connector with Safety

Step 6 - An electronic throttle control actuator is responsible for metering air flow into the engine which control engine RPM (revolutions per minute.) Using a throttle control sensor located near the foot pedal supplies feedback data to the computer. The throttle control system is integrated into the ABS, cruise control and traction control systems. In older vehicles throttle action was performed by a manually controlled throttle cable, which was actuated by the drive's right foot.

Electronic Throttle Actuator


Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2015-01-07)