In prepared testimony to be delivered to the House of Representatives Energy and Commerce Committee, Barra also will say that Kenneth Feinberg, who is overseeing the creation of a compensation fund, will have "full authority to establish eligibility criteria for victims and determine compensation levels.''
The defective ignition switches in older model Chevrolet Cobalts, Saturn Ions and other GM models have been linked to at least 13 deaths.
Barra testified to the panel in early April and was unable to answer many of the lawmakers' questions. She promised to come back after the company's internal investigation was completed.
Barra announced the results of that investigation earlier this month.
It outlined a long series of failures by GM personnel to take the ignition switch problem seriously and she promised to improve the company's performance and practices.
For more than a decade, GM engineers and others knew that the ignition switch had design problems. Those problems can cause GM cars to stall, which disables air bags and causes power brakes and power steering systems to malfunction.
Anton Valukas, who headed GM's internal investigation, will also appear before the House panel on Wednesday.
In his prepared testimony, he will say that "GM engineers were fully aware of this problem but did not consider it a safety issue."
Valukas' testimony portrays that shortcoming as "amazing."