Originally Posted by slimtim
I thought there would be way more people on here that had dabbled in self diagnostics...
I do, but only on VW and Audi. There is a fantastic piece of software called VCDS (previously VagCOM) for the VAG marque only, which communicates with all modules in the car. Whilst you can't reset the mileometer, you can read fault codes and also recode many units to adjust their operation, reset imobilisers for new keys, adjust reversing sensor sensitivity, change functionality of steering wheel buttons etc etc.