U.S. safety regulators are investigating the potential for air bags to fail because of software issues in older Chevrolet Impala sedans made by General Motors Co (GM.N), after receiving a consumer complaint about an alleged incident in Texas. The National Highway Traffic Safety Administration said Friday that it has opened a probe into about 320,000 Impalas from model year 2008, but would also look at 2007 and 2009 models. GM has recalled nearly 15 million vehicles this year, including the Impala, for ignition switch issues that could cause air bags to fail in a crash.