Carbon monoxide is a colorless, odorless gas that can cause permanent brain damage or death.
Toyota will add the engine shutdown function to most of its model years by 2020 .
The company would not comment on whether past events had any impact on the company's decision to add the feature. Toyota said the keyless ignition systems in the cars today meet or exceed all relevant federal security standards.
This type of error is particularly easy to make in hybrid cars, since the petrol engine in a hybrid often does not run when the vehicle is not moving. It can make it difficult to tell if the car has been shut down. If it does not, the petrol engine will start up after a short while, as the car's batteries start to lose their charge. It can even happen in non-hybrid cars, as many cars today have very quiet engines that are almost inaudible at idle.
Key-free ignition allows drivers to start their cars at the touch of a button as long as the remote fob is with them inside the car. This feature has been offered in the US market since the beginning of the 2000s and is now very common on new cars. Many new car models do not even offer the option of a key ignition.
The company would not say how long the engine could stay on before it automatically shut down.
Toyota will also add more noticeable warning sounds and visual alerts to its new models to ensure that the driver is aware that the engine is turned on when leaving the car, the automaker said. In the future, drivers will also have the opportunity to be notified via a smartphone app that the car is still on.
Toyota cars have received "engine on" warnings since 2003, the automaker said in its announcement. These new alerts will be "enhanced" with the high audio alerts.
Toyota will also add features to any vehicle that automatically switches it into the park when the vehicle is switched off. This system will only be available on vehicles with electronic gear shifters rather than mechanical levers.
Toyota has no current plans to add these features to previous models, a spokeswoman said.