GM Defects: New documents shed light on what company knew and when it knew it

The crashes General Motors has linked to its faulty ignition system often involve airbags not deploying after keys suddenly turn to the off or accessory position.

An October 2012 message from lead switch engineer Ray Degiorgio reads: "If we replaced switches on ALL the model years...the piece price would be about $10.00 per switch...based on...1.5 million units total."

"This inexpensive car is probably going to be the most expensive car GM ever made," said Rep. Tim Murphy (R-Penn.), who heads the House investigation.

At House and Senate hearings last week, GM CEO Mary Barra said she never knew about the defect until shortly after she took her new job in January.

The documents show an email was addressed to Barra in 2011 about a government investigation into steering issues in Ions and Cobalts, the primary problem cars, telling her: "This situation has been evolving."