Shares in Toyota have jumped nearly 5% after a US inquiry into reports of “unintended acceleration” found no electronic flaws in the company’s cars.
The 10-month investigation ordered by the US Congress followed recalls of millions of Toyota vehicles in 2009 and 2010.
Part of the investigation, published in August, suggested driver error might have played a part in many incidents and Toyota, still the world’s biggest car maker, welcomed Tuesday’s findings.
The company, which has reported a 39% drop in quarterly profits, lifted its operating profit forecast for the year to 550bn yen (£4.1bn; $6.7bn) from 380bn yen.
“Toyota still has a challenge competing against its rivals in emerging markets but there are hopes that it can regain its market share in the US market,” Mitsushige Akino, a fund manager at Ichiyoshi Investment Management, told Reuters news agency.
Toyota shares jumped 4.7% in early trading in Tokyo on Wednesday while they gained by more than 4% on Wall Street overnight.
“We believe that the results of the US Department of Transportation’s investigation confirms the reliability of our electronic throttle control systems,” Toyota said in a statement.
“We intend to continue to listen to our customers even closer and to offer not only safe vehicles but vehicles that provide peace of mind.”
The company recalled more than 12m vehicles globally in 2009 and 2010 for various problems including faulty floor mats, sticky accelerator pedals, braking software glitches and steering malfunctions.
Questions had been raised over whether software-driven throttles had played a role in unintended acceleration complaints but US Transportation Secretary, Ray LaHood, said in a statement on Tuesday: “There is no electronic-based cause for unintended high-speed acceleration in Toyotas.”
Mechanical flaws that were fixed in previous recalls appeared to be behind the problems with unintended acceleration, US officials said.
“We feel that Toyota vehicles are safe to drive,” Mr LaHood stated.
Mr LaHood said the US transportation department had been assisted by engineers from US space agency Nasa in its investigation into the recalls.
Nasa “rigorously examined” nine Toyotas driven by consumers who complained of unintended acceleration and reviewed 280,000 lines of software code to look for flaws that could have caused the acceleration, Mr LaHood said.
Engineers also used electro-magnetic radiation to test whether they could force the cars’ electronics to speed the vehicles up.
Despite the investigation’s findings, Mr LaHood said the National Highway Traffic Safety Administration (NHTSA) was considering new regulations to improve safety.
The new measures could require brake override systems, standardising keyless ignitions and requiring event data recorders, known as black boxes, to be fitted on all new vehicles.
Officials said they would also continue to carry out research on electronic control systems and a review of the placement of accelerator and brake pedals.
Toyota paid the US government a reported $48.8m (£30.3m) in fines over the handling of the recalls.