Software bug stalls Toyota hybrid cars

Toyota is recalling 160,000 of its Prius cars because of bugs in the software controlling the hybrid petrol/electric engine system that can cause the warning lights to come on without cause.

The issue occasionally causes the system to shut down the vehicle's petrol engine, the manufacturer admitted.

The US National Highway Traffic Safety Administration has so far received 428 complaints about the software problems.

Toyota stated that, because the Prius is equipped with an additional electrical engine, drivers will be able to get off the road safely and that restarting the engine will usually solve the problem.

Water getting into the engine is one of the factors blamed for the engine shut downs.

Toyota has sold about 15,000 Prius cars in Europe, 75,000 in the US and 70,000 in Japan. The company is the largest maker of hybrid cars, ahead of Honda and Ford.

A hybrid car is equipped with petrol and electric engines. When the car brakes, the kinetic energy is converted into electricity and stored in a battery. This power is then used to move the vehicle at low speeds of up to 25 mph.

At higher speeds the petrol engine takes over, which operates less efficiently at lower speeds. The technology improves fuel efficiency by roughly 50 per cent over a non-hybrid.

The recall appears to be the first for a bug in the hybrid system. Although modern vehicles already incorporate dozens of microprocessors, the hybrid engine technology makes cars even more reliant on chips and software.