Nearly four million Nissan cars are being recalled due to major safety problems where passenger air bags or seat belts could fail in a crash, leading to serious injuries or fatalities.

Nissan North America said that 3.2 million cars may have a problem with a sensor that detects if the front passenger seat is occupied and if that passenger is an adult or a child.

Defective sensors might incorrectly think that an adult is a child or classify the seat as empty, thus turning off the air bag.

The 2016-2017 Nissan Maxima is among the cars being recalled over safety fears (Andrew Burton/Getty Images)

The two recalls are just the latest in a string of safety problems to hit automakers in the past year with Acura, BMW, Chrysler, Ford, Honda, Lexus, Mazda, Toyota and other manufactures having to recall cars over air bag problems. The Nissan problems are unrelated to the other air bag issues.

The recall applies to certain cars of the following models: the 2016-2017 Nissan Maxima, 2013-2016 Nissan Altima, NV200, LEAF and Sentra, 2013-2017 Nissan Pathfinder, 2014-2016 Nissan NV200 Taxi, Infiniti QX60 and Q50, 2014-2017 Nissan Rogue, 2015-2016 Nissan Murano, Chevrolet City Express and 2013 Infiniti JX35 vehicles.

Nissan is also recalling another 620,000 of its 2013-2016 Sentras, because of issues with the air bag sensor not turning off when it is supposed to (David McNew/Getty Images)

Nissan will notify owners of the problem and offer to fix it for free, however no schedule has yet been provided for when these notices will go out or how quickly the repairs can be made.

Nissan is also recalling another 620,000 of its 2013-2016 Sentras. In these cars, the air bag sensor has the opposite problem: It isn't shutting off when it should be.

The automaker said the front passenger seat belt bracket may become deformed if it is used to secure a child restraint system. That deformed seat bracket might then cause the air bag not to shut off when it should be off.

Nissan has not yet figured out how to fix the problem and is warning owners not to install child restraint systems in the front seats.

It will take Nissan more than a month to notify owners of the problem and then the carmaker will follow up with a second letter once it figures out a solution, which will be free.