Tesla is rolling out an over-the-air upgrade to its model S series that will allow them to steer and park automatically.
However, users have posted videos online that show the new autopilot feature exhibiting dangerous behaviour.
One Miami diver said that the car drove at 75mph in a 60mph zone which resulted in a police stop and eventual speeding fine.
Elon Musk, chief executive of Tesla, said the new feature is still in development and warned drivers to keep hold of the steering wheel when the autopilot mode was engaged.
"We're being especially cautious at this stage so we're advising drivers to keep their hands on the wheel just in case," he said.
"Over time there will not be a need to have your hands on the wheel. We're very clearly saying this is not a case of abdicating responsibility, that will come at some point in the future but ... this is still early days."
The new feature is accessible for cars built after September 2014 and is available to United States customers now while European and Asian owners must wait another week.
Tesla noted that the system has safeguards in place to avoid accidents. In more difficult navigating conditions, an audio alert will come on and if that is ignored, the car will slow and eventually stop.
Reporters who took Model S sedans for test drives said that a notice saying ‘hold steering wheel’ illuminated on the dashboard when they took their hands off the wheel.
Musk estimates that within three years, cars will be able to drive "from your driveway to work without you touching anything," but regulatory approval could take years.
The autopilot system is expected to improve the more Model S drivers use it.
"The whole Tesla fleet acts like a network. When one car learns something they all learn it," Musk said.
"As more people enable autopilot, the information about how to drive is uploaded to the network. Each driver is effectively an expert trainer in how the autopilot should work."
Last month, the electric vehicle manufacturer unveiled an electric SUV dubbed 'Model X' which is capable of driving for 250 miles between charges.