The National Highway Traffic Safety Administration (NHTSA) have opened up a defect investigation into 2006 Toyota Highlander hybrid electric vehicles (HEV) after receiving 32 complaints of stalling engines. None of the incidents resulted in an accident, but many complained that the vehicle could not be restarted and had to be towed to the dealership. The NHTSA have carried out several investigations into stalling engines of different vehicles and manufacturers over the years, many of which have led to recalls.