Safety first! Don't do anything that could cause harm to yourself or others. Keep in mind that a vehicle has several systems like airbags that could cause serious injury when misused. If in doubt, let it be.
If you work on a vehicle, don't try anything that could interfere with road safety and don't experiment on public roads. Only perform testing in a safe place with a stationary vehicle.
Use special caution when interacting with safety-critical devices such as brake systems, steering components, the engine or high voltage components like the car battery.