to make sure that data's flowing but beware it might (temporarily) screw up your shell. if you get weird chars, just restart the term and it's fine again, or pipe it to less which displays them correctly. (or use nc / netcat if you have)
it's not a solution, but at least you can see if things are wrong on the hardware level.
i'd be interested on your progress on linux-odbII and what you're able to do with it.