An engine diagnostic is a test which is performed to learn more about why an engine is not functioning properly. Engine diagnostics can be performed by skilled home mechanics with the proper equipment, or a car can be taken into a mechanic or dealer for diagnosis. The engine diagnostic is used to gather data which can be utilized in the repair of the vehicle
Performing an engine diagnostic starts with plugging a device into the car’s onboard computer. There is usually a space to do this just under the dashboard on the driver’s side of the car. The device interfaces with the computer, returning a diagnostic code which can be referenced against a list of codes for vehicles from that manufacturer. If the engine is in good working condition, the device will inform the user. If there is a problem, one or several codes may be displayed.