Assuming a gas car, fuel lines running under the floor. Or the roof-mounted sensors to render the computer blind.

Assuming I owned a self-driving car (rather than renting one), I'd probably also put in a switch that disconnects power to the main fuel pump or the motor contactor in case of an electric car. Everything needs a Big Red Button(tm). Dave Bowman lobotomizing HAL-9000 one circuit board at the time, is one of my favorite movie scenes.