Corvette CCM Reverse Engineering Anyone?

[NomakeWan]

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.

The one I'm using for this experiment is an Arduino Mega 2560. I had it laying around from jury-rigging my furnace after several botched repairs by a local HVAC company. Ended up with a completely new HVAC system this summer, which freed the Mega up for more experiments. EDIT: Oh, and I'm using Hardware serial. I'll use Software if I have to, but running the numbers the hardware should have no problem going to 8192 Baud; there's only 0.1% error at that baudrate with a 16MHz clock.

I will say I completely forgot that the CCM has a VSS line. D'oh. That's probably exactly what drives the speedometer considering I don't recall anyone with aftermarket ECMs mentioning the speedometer doesn't work. I'll still see what happens when I change the reported VSS value, but then I'll set it back to 00 and change the coolant temperature value instead.

I'm catching up on my reading, and just had time to digest this. I'd love to know where you found this, but will understand if you'd rather not share.

Edit: NomakeWan - is 128209 in the ballpark for odometer on your '95 when you dumped it last? How about 124880 back in April 2020 when you first dumped it?

Sadly because I acquired this information from another source, I cannot actually share the complete document. I wish I could. But if it's just information about mode requests, those I can at least crop and screenshot that.

You are right on the money with the odometer; it presently reads 128216 and has not changed since I took the latest log. This also confirms the "within 6 miles" inaccuracy of that register as quoted by the guys on the Corvette Forums.