I have an Audi tt 2003 and was wondering if there's a command set or hex values to send to the various modules in the car on the k-line.  For example I want to retrieve the fault codes stored within the TCM,ECM or the ABS etc. I know there are obd code readers  out there that can do this however I would like to write my own application in Csharp.  I'm thinking about installing a touch screen and converting the climate control and radio switches to touch screen module as well. But I'm not sure quite how this k-line works.