The modules that help control the airbags and seat belt pretensioners in a crash aren't working in 4 million GM vehicles, prompting a massive recall that includes the GMC Sierra 1500/2500/3500, and Yukon. GM received an internal report in May relating to the crash of a 2014 Chevrolet Silverado where the driver’s frontal airbag and seatbelt pretensioners were alleged not to have deployed.
GM opened an investigation into the issue in June and contacted Delphi, the supplier of the sensing and diagnostic module. The automaker gathered additional electronic data recorder records from other incidents where the same crash symptoms occurred.
The modules will need to be reprogrammed, GM just doesn't know when yet.