As far as I know, GTA Online doesn’t have a dedicated car diagnostic feature like a real vehicle does. You can still get a basic idea of your car’s condition by looking for visible damage, smoke, or changes in how it drives, but the game doesn’t provide a detailed scan for specific mechanical faults. In real life, a car diagnostic tool can read trouble codes and spot problems that may not be obvious while driving. GTA Online keeps this system pretty simple, with most vehicle damage and repairs handled through the available service options.