Modern OBD implementations shows you limited amount of information. For example you can not get or clear trouble codes of AirBags.
VAG has own diagnostic VW TP "language" over OBD2. The VW TP useful for:
1) Diagnostics AirBag, Engine, Transmission, electronic components etc.
2) Setting up new and configure installed equipment.
In last version of the OBD Scanner we have implemented trouble code scanner for VAG. Our approach is trying to read known VAG modules over VW TP and try to read unknowns using UDS (Unified Diagnostic Services) method. For each detected unit we run a diagnostic tests and read detected trouble codes. Diagnostic methods has low priority, so some modules just ignore diagnostic requests. The best way to diagnose is turn ON key but do not start an engine. For best results you should try to scan few times. Each scanning takes about 15 minutes depends on amount of detected modules. After successful scanning you will get a report. You'll see detected trouble codes for each module and description.
To delete detected DTC first complete scanning. The engine should be OFF but the key should on first position (ACC).
Some DTC can be deleted only if the engine is not running.