CAN frames are not standardized. You cannot have a single command to do operations on any car. Each manufacturer has different bit patterns and also it varies between car models. Atleast with Chrylsers I know its true. There should be a lookup based on the car's model with a unified API which I think will happen soon based on the pace of car tech progress. Also note that once the frame is on the bus, it get executed and an ACK will be sent. There is no authentication mechanism in place. So once you put a frame into the CAN bus, there is no way to stop it. This will be the top pain points for car techs to fix.