cog symbol

hey guys, pretty new here, so hopefully i get good feedback. my cog symbol just came on and i hope its not a tranny issue. my brother drove my car(only drove stick cars) and decided to mess with the 234 since im auto. he downshifted bad but and kinda of made the car abrubtly stop, so i told him to stop. on our way home it came on, we turned the car off and on and it was gone. it came on before since my catalytic converter is done, so my first 3 gears were sluggish and set the symbol once or twice when it did that. do you guys think he mest up my tranny or is it still from my bad converter and bad cam shaft sensor? please i really dont want to sell this car, tranny has 60k on, HELP!!! please and thank.