Greg Gardner

Detroit Free Press

General Motors on Friday recalled more than 4 million vehicles, most of them in the U.S., to fix an air bag software defect that has been linked to one death and three injuries.

In rare cases, the car's sensing and diagnostic module — a tiny computer that senses what the vehicle is doing and controls air bag deployment — can go into test mode, the company said. If that happens, the front air bags won't inflate in a crash and the seat belts may not work either.

The company learned of the problem in May when a 2014 Chevrolet Silverado crashed and its air bags didn't deploy. GM notified Delphi. The two companies tested the modules and decided to recall the vehicles last week.

GM will notify customers and update the software for free. Dealers already have access to the software update so they should be able to repair the vehicles quickly.

It was the second large recall in two days from a major U.S. automaker. Ford expanded on Thursday an existing recall from about 900,000 to nearly 2.4 million over a potential door latch malfunction on six models from between the 2012 through 2015 model years.

Ford has identified one accident and three injuries related to the defect.

While the Ford recall covered fewer vehicles, the cost led the company to cut its 2016 profit forecast, before taxes, by $600 million to $10.2 billion.

► Related: Ford recalls 1.5M more vehicles for faulty door latch

The GM recall is large, but the repair involves a software update rather than a mechanical change. Vehicles involved in the recall are from the 2014-2017 model years and include models from Buick, Chevrolet, GMC and Cadillac.

Unlike the notorious series of ignition switch recalls in 2014 — for which the company paid more than $2 billion in damages, victim compensation, regulatory fines and a criminal investigation settlement — this recall was voluntary and does not appear to involve a failure to respond to reports of serious injuries or one reported fatality.

On the website of the National Highway Traffic Safety Administration the regulatory agency lists 17 vehicles for which an owner filed some notice or complaint. The recall includes 4.28 million vehicles worldwide, 3.6 million of them in the U.S.

But in a statement, the automaker said the cost of this recall is not expected to be material and will be included in GM’s third-quarter earnings when those are reported in late October.

This is unrelated to the ongoing record recall of air bags made by Japanese supplier Takata that now affects more than 20 million vehicles from more than a dozen manufacturers. These air bag modules were supplied by Delphi Automotive and made at a plant in Kokomo, Ind., according to NHTSA documents.

The affected vehicles are:

2014-2016 Buick LaCrosse, Chevrolet SS, Chevrolet Spark EV

2014-2017 Buick Encore, GMC Sierra 1500, Chevrolet Corvette, Chevrolet Trax, Chevrolet Caprice police car and Chevrolet Silverado 1500

2015-2017 Chevrolet Tahoe, Chevrolet Suburban, Chevrolet Silverado HD, GMC Yukon, GMC Yukon XL, GMC Sierra HD, Cadillac Escalade and Cadillac Escalade ESV.

Contact Greg Gardner: 313-222-8762 or ggardner@freepress.com. Follow him on Twitter @GregGardner12 The Associated Press contributed to this report.