Vehicle diagnostics means reading out a car's electronic control units via the standardised OBD interface, making stored fault codes, sensor data and system statuses visible. This lets you quickly find out, for example, why the engine warning light is on, without having to take the vehicle apart. For beginners, the topic is often confusing – this guide explains the basics simply and clearly.
What exactly does a diagnostic tool do?
A diagnostic tool connects to the vehicle's control units via the OBD port and reads out their stored data. This includes fault codes (so-called DTCs), live readings such as engine temperature or RPM, and – depending on the device – service functions such as resetting maintenance intervals or teaching in new components. So a diagnostic tool doesn't just show THAT a fault is present, but often also WHICH component or system is affected – the basis for a targeted repair instead of guesswork.
Since when has OBD2 been mandatory?
In the EU, the OBD2 interface has been legally required since 2001 for newly registered petrol cars and since 2004 for diesel cars. Since then, all new cars have had to feature this standardised connector, through which emissions-related and many other control units can be read out. Practically every car built since the early 2000s can therefore be read out with a suitable diagnostic tool, regardless of manufacturer.
Can I diagnose it myself, or do I need to go to a workshop?
Any vehicle owner can read out fault codes and use simple diagnostic functions themselves with their own diagnostic tool, without being a trained car technician. For pure fault diagnosis – identifying which component is causing a problem – a standard diagnostic tool and a bit of reading time are completely sufficient. More complex work such as mechanical repairs, safety functions (e.g. airbag or brake system work) or control-unit coding that affects vehicle registration, however, still belong in the hands of a qualified workshop.
Do I need my own diagnostic tool?
Your own diagnostic tool is worthwhile for anyone who regularly checks their vehicle themselves, wants to narrow down fault causes in advance, or wants to save on workshop costs. The advantages at a glance:
- Cost savings: instead of paying for a chargeable workshop diagnosis for every warning light, you read out the fault yourself – the purchase often pays for itself after just a few uses.
- Time savings: no workshop appointment and no waiting required to find out what a warning symbol means – the diagnosis often takes only a few minutes.
- Your own oversight: you keep track of your vehicle's technical condition, spot recurring faults early, and can already know what's going on before every workshop visit.
A look at our Universal Diagnostic Tools PKW is especially worthwhile for beginners: there you'll find devices used both for private use and in independent workshops.
Recommendation for beginners
These two diagnostic tools are particularly suited to getting started – easy operation, broad vehicle coverage and a fair price-performance ratio:
Vident iSmart600 Max Car Diagnostic Tool with ECU Coding
A solid entry-level device with an ECU coding function that goes beyond classic fault diagnosis to allow simple control-unit adjustments too. Price: €349.00. 
Vident iAutomaster-Pro Diagnostic Tool with Lifetime Updates
With lifetime updates and no subscription costs, this is a particularly long-term, plannable choice for beginners who want to use their diagnostic tool for many years. Price: €499.00. 
So vehicle diagnostics doesn't need to be a book with seven seals: with the right diagnostic tool, most fault messages can be read out and classified yourself, while genuine repair work still belongs in expert hands. If you have questions about choosing the right device, our team will be happy to advise you personally on 0711-3654 4645. Buy now, pay later is available via Klarna or PayPal.