Nissan said Wednesday it would recall almost a million cars in the 2013 and 2104 model years, to fix a potentially disastrous defect that could cause air bags to fail in an accident. Nissan said in a statement that it first became aware of the problem in February of last year and ordered a fix then.\nOwners of the approximately 990,000 cars affected by the recall will start receiving notices sometime in April. Nissan notified the National Highway Traffic Safety Administration that the company knows of three accidents in which passenger-side air bags did not inflate during collisions.\nFaulty Software May Not Detect If Passenger Seat Is Occupied\nThe problem turns up in a federally mandated safety system that uses computer software to detect if the passenger seat is occupied or empty, or occupied by a small child. If the seat is empty or is taken by a vulnerable child, the air bag will not deploy.\nBut the software may not realize that someone is sitting in the seat if there is “high engine vibration at idle” when a passenger gets in the car, or even if the passenger sits in an unusual posture in the seat. In that case, the software may not detect that someone is sitting there and would consider the seat empty.\nThat means in a collision the air bag would not inflate, cushioning the passenger form serious impact with the dashboard.\nRecall Affects Eight Different Nissan Models\nThe models that Nissan said it would recall cover most of the automaker’s line. They are:\n • 2013-2014 Nissan Altima — 544,139 vehicles recalled\n • 2013-2014 Leaf — 29,165\n • 2013-2014 Nissan Pathfinder —124,202\n • 2013-2014 Nissan Sentra — 182,569\n • 2013 NV200/Taxi — 6,696\n • 2013 Infiniti JX35/ 2014 QX60 — 63,698\n • 2014 Infiniti Q50 — exact quantity of recalled vehicles not announced.\nNissan said that despite the three accidents in which air bags in cars now targeted for recall failed due to the software defect, it hasn’t heard of any injuries or fatalities connected with the problem.\nThird Air Bag-Related Recall In Past Year\nJust a week ago, American automaker Buick recalled 1.8 million vehicles to fix an air bag defect. And almost exactly a year ago, Nissan itself recalled almost 90,000 cars due to a problem with a sensor that could cause air bags to fail.\nOnce the recall gets underway, Nissan owners simply take their cars into nearby dealers who will recalibrate the airbag software for free, to properly detect a passenger in the seat.