Last year, Nissan issued a recall to fix a flaw in the airbag control systems on almost one million vehicles. However, after many reports of continued failures in these systems even after repairs U.S. regulators are now looking into whether or not the recall actually fixed the problem.

The National Highway Traffic Safety Administration opened the query on March 18, citing 124 complaints filed by motorists after the recall began last April. The affected vehicles are model year 2013-14 Nissan Altima, Pathfinder, Sentra and Leaf; 2013 Infiniti JX35, 2014 Infiniti QX60 and Q50, and the 2013 Nissan NV 200/Taxi vehicles. Some drivers have even alleged that the flaw continues even after multiple repairs by Nissan dealers.

"Nissan Group believes the recall remedy was effective and appropriately addressed the safety defect," a spokesman at Nissan North America Inc., Steve Yaeger said Sunday. "Nissan and Infiniti also took additional steps to help dealers address residual customer concerns unrelated to the recall and to maintain high level of customer satisfaction."

Nissan issued a recall last year of 989,701 vehicles, saying that the software may incorrectly classify the passenger seat as empty even when it is occupied by an adult. This flaw could potentially lead to the failure of the airbag to deploy during a crash leading to an increased risk of injury to the passenger.

At the time the company identified two accidents in which the airbag failed to deploy, according to NHTSA documents, but a Nissan spokesman said the company was unable to draw any conclusions about that being related to the software issue.

Airbag recalls have plagued the automobile industry since last year. Fiat Chrysler Automobiles NV, Honda Motor Co. and Toyota Motor Corp. recalled 2.1 million vehicles in January because of airbags that go off while driving. In February, Jaguar Land Rover in North America said it would recall more than 61,000 vehicles because some passenger-side airbags may not open on impact because of faulty software.

Nissan has reacquired four vehicles for testing. Among the complaints received by the NHTSA, one Pathfinder owner said his airbag sensor continued to fail to recognize his 112 pound wife even after undergoing the recall repair.

"That puts my wife in jeopardy in the event of a head-on collision," the complaint said. "I was told there is nothing they can do."

The query on Nissan "will look into the effectiveness of the recall remedy and whether any other OCS-related problems exist in the recalled population," NHTSA said in the advisory, referring to the Occupant Classification System algorithm.