Actuators receive signals from the powertrain control module and carry out adjustments needed based on the data the PCM received from the sensors.

The battery supplies the power necessary to start the engine when the ignition switch is is turned on.

The fluid reservoir stores the brake fluid that the master cylinder uses to maintain hydraulic pressure.

The lubrication system lubricates engine components by putting an oil film between them to reduce friction and smooth engine operation, cools by absorbing heat from engine parts, seals the pistons and cylinders to contain combustion, cleans contaminants, and quiets engine noise.

The transmission provides the appropriate power to vehicle wheels to maintain a given speed. The engine and the transmission have to be disconnected to shift gears and a manual transmission requires the driver to manually manage this disconnection (using a clutch) and to manually shift gears. An automatic transmission is essentially an automatic gear shifter and handles this process without driver input.