The dealership will often charge you like $60 USD or more just to find out what's wrong when a vehicle or repair isn't covered under warranty. The next time you need a diagnosis (for example, if you have a “Check Engine” or MIL light on 🔆), head to a nearby auto parts store and they'll probably be able to do a generic scan for free as a first-step.
It's at least a place to start if you have the time to spare. — Or, you can try to track down or purchase vehicle-specific scanning and software tools, such as VAG-COM for Volkswagen/Audi vehicles.