[mhandley]

Is CAN bus actually a serial bus? If so, I wonder if it's possible to make a CAN bus jammer. Plug it in anywhere on your car, and its sole role is to detect all CAN bus messages and jam them. Add bluetooth to it, so you can switch it on and off from outside the car.

[wildzzz]

CAN is multi-master so you could just have a device on the bus that hold the line active forever.