Also in the dock will be the US auto safety agency, the National Highway Traffic Safety Administration (NHTSA), under attack for not acting on its own evidence that the ignitions posed dangerous risks to drivers.
The hearing is the first in what is likely to be a mounting pile of legal troubles for the US auto giant, including a Justice Department probe and lawsuits from people injured and families of those who died in crashes allegedly tied to the ignition issue.
Analysts have already speculated that the trouble could cost the company billions of dollars in penalties and damages, on top of the huge costs of the recalls themselves.
In prepared testimony to the investigations subcommittee of the House Energy and Commerce Committee, Barra, a lifetime GM employee, said she still does not know why it took years for the automaker to act on the ignition problem.
But she pledged to find out, and to be "fully transparent" with the answers.
"More than a decade ago, GM embarked on a small car program. Sitting here today, I cannot tell you why it took years for a safety defect to be announced in that program," Barra said in her prepared remarks released in advance of the hearing.
"When we have answers, we will be fully transparent with you, with our regulators and with our customers."
She said management would be "fully accountable" for the issue, and that GM "will do the right thing," though what that entails is not clear.