Making a correction BEFORE EFILING

I filled my taxes myself thru turbotax,  upon reviewing a error was found,  I have NOT e-fled yet,  but I can't seem to find where to go to fix the issue. I need to change the amount of my car depreciation because it is stating it is too large. I don't even recall doing that section of my taxes, let alone entering the amount, And I cannot e-file until I correct.  I cannot seem to find where to go to correct it.  PLEASE HELP!