Do you have any mods installed? I had this issue when I was playing with an unofficial texture mod.
In the game's installation folder (by default Program Files - Mass Effect), go to BIOGame - Config. Make sure DefaultEngine.ini is there.
If it's not there, you may want to either repair or reinstall the game. To repair the game in Steam, right click the game and go to properties. In the local files tab, select 'verify integrity of the game cache'. In origin, you can repair the game by right clicking and selecting the repair option.
If it's neither of these versions, I think you'll have to reinstall.
