Sounds neat. I'd be interested to hear how the speedometer functions. My guess would have been that the ccm uses the vss line from the pcm for that instead of aldl data.

Mind me asking what arduino you're using? Hardware or software serial? Around 2009 or 2010 I messed around with the mpguino project and got it talking to my VW over iso 9141. I recall building an op-amp setup for that, but I can't find the code. I know I have the parts and schematic stashed in an esd bag in my lab somewhere.