I have 2 Crash Data Retreival (CDR) machines at work. That is the only way to read most Event Data Recorders "black boxes" in cars. The only reason to have a CDR is to do accident investigation. Almost nobody except police and independent reconstruction firms have one. The full kit is about $8k and software runs about $1200 a year.

They are NOT mandated by the Feds. In 2013 the Feds made a minimum list of data a company had to store IF THEY CHOSE TO HAVE AN EDR.

Suprisingly some high end vehicles like BMW and Benz only started putting these in cars recently. GM started in the mid 90s.

Chrysler does have one of the more comprehensive data streams in theirs, including tire pressures and steering wheel angle.

Most EDR data is stored in the Airbag control module. There are some Fords that also save info in the PCM.