Recalls are more or less a pain for everyone involved. As the owner, you’re inconvenienced because your car should be safe and when a recall occurs you have to take it to a dealer for repairs. Once those repairs – which can take months to occur depending on the availability of parts – are finished, drivers have a reasonable expectation that their car is fixed. But that apparently wasn’t the case for nearly a million Nissan and Infiniti vehicles now under investigation by federal regulators.

The National Highway Traffic Safety Administration announced over the weekend that it has opened an investigation into Nissan recalls covering more than 990,000 vehicles.

Nissan’s original recall of model year 2013 to 2014 Altima, Pathfinder, Sentra and LEAF vehicles; model year 2013 Infiniti JX35; model year 2014 Infiniti QX60 and Q50; and model year 2013 Nissan NV 200 and Taxi vehicles was initiated last year after the company became aware of issues with the Occupant Classification System (OCS), which uses sensors to identify an occupant in the passenger seat.

At the time, Nissan said software in the vehicles’ OCS may not detect an adult in the passenger seat, resulting in the non-deployment of airbags in the event of a crash. To remedy the issue, Nissan said it would update the affected vehicles’ OCS software.

According to a NHTSA notice [PDF], since the recall was initially announced, the agency has received 124 complaints from consumers alleging issues with the OCS after having their vehicles repaired at Nissan or Infiniti dealers.

The majority of complaints alleged the passenger airbag status light stays on – indicating the passenger airbag is turned off – even when an adult passenger is present in the front seat.

“While traveling 40 miles per hour, the airbag warning light illuminated,” one consumer tells NHTSA. “The vehicle was taken to the dealer where it was repaired under [the recall]. However, the airbag warning light remained illuminated.”

Some vehicle owners tell NHTSA that dealers have made multiple repairs to the cars but the problem persists.

“The passenger airbag turns off when a passenger is in the seat,” one complaint states. “It is not always immediate and does not happen every time it is driven. It has had two recalls from this issue and this will be the eleventh time it has been into the dealership for this same thing.”

NHTSA says that it has received no reports of injuries or accidents as a result of the issue.

The agency opened a “recall query” into the issue to determine the effectiveness of the recall remedy.

Nissan has been party to a number of NHTSA investigations over the past 12 months. In January, regulators opened an investigation into nearly 195,000 model year 2013 Nissan Rouges after receiving complaints alleging the airbags deployed up to a minute after crashes and either inflated slowly or didn’t inflate fully.

Prior to that in November 2014, NHTSA opened an investigation over the loss of power steering in 17,000 model year 2008 Infiniti EX35 compact crossover vehicles.

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