What is OBD2 (on-board diagnostics)?

OBD2 stands for on-board diagnostics (second generation), and is a communication system for a vehicle to show diagnostic and reporting data. It's been standard on all cars since the mid-1990s. To use OBD2, you'll need to locate your car's OBD2 port – usually found under the dashboard – and connect an appropriate OBD2 reader to the port.

Through this connection, you can check any fault codes that the car's flagged up which might be causing a check-engine light. This will help point you towards the problem rather than blindly guessing where the issue is. You can also monitor various engine and car data points in real time depending on the OBD2 reader you're using.

Some OBD2 functions and codes can only be shown with manufacturer-specific hardware, so you might find that a generic OBD2 code reader can't show you all the data you're looking for.