Federal officials will investigate a potential flaw in GM vehicles that may have caused airbags to fail to deploy in thousands of fatal crashes.
GM has already recalled millions of cars because of ignition problems that shut off power steering and brakes and deactivated airbags. That design flaw has been linked to at least 13 deaths, and GM has pledged millions to compensate victims.
The new investigation by the National Highway Traffic Safety Administration (NHTSA), announced Friday, springs from a request from an automobile safety expert who says he believes there may also be a problem with the algorithm that tells the airbags in many GM models when to deploy.
Donald Friedman, a former NHTSA contractor who has testified as a paid expert witness for the plaintiffs in suits against GM, sent the agency a letter in November alleging that the defect "results in the inaccurate suppression of the front passenger airbag moments prior to the frontal impact/crash on (most) model year (MY) 2004-2010 GM models."
Friedman asked the agency to investigate, based on information from a 2011 crash in Texas involving a 2008 Chevrolet Impala in which an elderly couple was injured. The passenger side airbag didn't deploy, according to Friedman, because Roberto Martinez, who was sitting in the front passenger seat, was jostled prior to impact and the car mistakenly computed his weight in the seat in that instant at 47 pounds rather than the roughly 170 pounds he actually weighed.
"The reason that the airbag did not deploy in this case is that it was not sensing the correct weight of the occupant … in the last second of 18 seconds worth of recorded data," Friedman told NBC News on Tuesday.
Newer model GM vehicles and other cars sold in the U.S. are equipped with sensors that monitor the weight on the front passenger's seat to prevent the airbag on that side from inflating if the occupant is a child. Airbags can kill young children riding in the front seat.
Roberto Martinez, a World War II vet, died several months after the crash. His wife, Aurora, who was driving the vehicle and survived the crash, filed a lawsuit in Texas state court in 2011 against GM and the GM dealership which had sold the car, alleging the vehicle's airbag system was defective and requesting damages. The court record lists a dismissal of the lawsuit in 2012. According to Manuel Guerra III, the attorney who represented Aurora Martinez, the parties settled and the terms of the settlement are confidential.
Friedman said he had found 42 cases of Impalas with airbags that didn't deploy in NHTSA's Fatal Accident Reporting System database, and 2,004 cases for all auto models from 2004 through 2010. He asked that NHTSA investigate all the fatal accidents to see if algorithm defects were a factor.
In announcing its investigation, NHTSA said it had received no other reports of problems with the airbag deployment algorithm and "did not find any defective trend with this allegation."
"However, in an abundance of caution regarding the performance of air bags in the nation's fleet, NHTSA is looking further into this allegation," it said. "The agency will review all available data and take appropriate action as warranted."
The software controlling the deployment of the airbag in vehicle the Martinezes were driving was manufactured by Delphi, Friedman said. In the Martinez case, the information about the algorithm was downloaded and reported by Delphi, and then publicly released, he said. Prior to this disclosure, Delphi's algorithm had remained confidential, he said.
Representatives of Delphi did not immediately respond to a request for comment from NBC News.
Friedman said in a second letter to NHTSA that the Martinez case was the first in which the algorithm had been examined by an outside party and found to be defective.
"We do know that millions of GM vehicles use this control module," wrote Friedman, "but do not know how many vehicles use the same or a similar algorithm, whether produced by Delphi or other manufacturers."
GM spokesman Alan Adler said the company would "cooperate and respond to NHTSA."