Can bus...

Hi!
Does anybody undestound how it works?
I buy this one,from here http://www.skpang.co.uk/catalog/arduino-canbus-shield-with-usd-card-holder-p-706.html but i recive empty data string from the can bus...how can i change value for my car that use standard iso 11898-2 and 1mbps canbus speed?

Cross posting - CAN BUS SHIELD,aiuto!!!???!!!!! - #4 by system - Device Hacking - Arduino Forum - :frowning: