Vehicle was never turned on.
The reference was a connector pin that measured GND but in the data plug. But you are quite right, the mains related ripple was a real problem.
No, it's actually not. Granted, it looks bad, but this is exactly the type of environment CAN was designed to function in.
a) CAN is a differential bus.
b) CAN-Hi and CAN-Lo go in different directions, and thus the polarity on your screen for one channel is wrong (CAN-Lo goes negative)
c) in the Recessive state, they're both the same (0), and in Dominant, their differential amplitude is doubled
d) that means the ripple, even of such large amplitude, will get canceled out, when the 2 channels are combined (in-phase noise is eliminated)
*) to clarify, CAN-Hi is Added to the inverse of CAN-Lo by a bus transceiver (or the Rigol decoder)
e) that's how you get the noise immunity required in such an environment, enabling reliable communications
Somehow, you've just got 2 copies of the same CAN signal, and that doesn't do you much good. Though you
can decode CAN with only one-side, as long as there is no noise. I've done it, but wouldn't recommend it, since "Seeing" even just 1 error (corrupted packet) in 1000 messages, that
isn't really there, doesn't enhance productivity.
Although many errors are shown, observation shows all data successfully decoded at some point.
I hate to have to say this, being as you're such a good guy and all, but you haven't decoded
any CAN data yet.
Like the last time you tried this, and wound up "decoding" the gaps between the packets, and unsurprisingly got all 00 "data".
I'd offer to set up the scope for you, but I don't have one here so I could walk you through the settings. Maybe if you email me airfare, I can hop a plane to NZ and show you how to do it.
Yeah, that's the ticket! (apologies to J.Lovitz, SNL)
"A" for effort, though.
Not everyone would be willing to explore unknown territory, as you have been.