The National Highway Traffic Safety Administration said Sunday it is opening an investigation into whether Nissan Motor Co.’s recall of nearly 1 million vehicles for air bag problems was effective.

The auto safety agency said it is reviewing Nissan’s recall in March 2014 of 989,701 2013-2014 Altima, Leaf, Pathfinder, and Sentra, 2013 NV200, 2013 Infiniti JX35 and 2014 Infiniti Q50 and QX60 vehicles because the occupant classification system software may incorrectly classify the passenger seat as empty, when it is occupied by an adult.

Since the recall was launched, NHTSA has received 124 complaints alleging problems with the system after the recall repairs and in some cases other OCS related repairs were made by Nissan dealers. “The majority of the complaints allege the passenger air bag status light stays on (i.e., indicating passenger air bag is turned off) for adult front passengers. Some of the complaints state the dealers have made multiple repairs but the problem still persists,” NHTSA said.

Unfortunately for countless car owners, recall campaigns are not always effective.

According to a series of news reports, one of Nissan’s many auto recalls is now under investigation by the U.S. National Highway Traffic Safety Administration. The investigation is associated with an issue that may have not been entirely fixed by the company, which may have prompted several consumers to report problems.

If the investigation concludes that the company needs another fix, Nissan may end up having to issue another recall.

The original recall was launched when Nissan learned that high engine vibration along with potentially unusual seating positions may have caused the Occupant Detection System software to fail. As a result, the system may not identify a person sitting on the passenger seat, thus increasing the risk of a serious personal injury.

The issue caused Nissan to recall over 82,000 vehicles. The models included the 2013 Leaf, Altima, Pathfinder, Sentra, and Infinity JX35.

According to federal regulators, the recall helped to push the number of warranty claims down. But according to the company itself, it never stopped receiving complaints associated with the ODS systems, even after the recall campaign. Toward October of 2013, Nissan claimed it was not able to identify the problem as a safety defect, even knowing the system may not correctly prompt the air bags in the event of a crash if the ODS does not recognize a passenger is occupying the system.

Before February of 2014, the company was able to come up with certain changes to the system that helped the company to develop better safety systems for newer models.

In spite of the changes, at least two incidents were associated with the passenger air bag not deploying in crashes.

If you would like to know more about this investigation, follow this link.