the codes are not always obvious (only visible when the code is 'active', the 'wrench light' shows there is a stored or historical code), and unless you have the "service" password (which gets changed to different numbers by different dealers/techs) you will not be able to clear the codes. some times you may get lucky by disconnection of the battery over night (not likely in my experience).
My suggestion in these cases [and what I have to do] always is to call the dealer's tech, pay the money, find out what the code is and what it takes to fix, and ask for the password, you may not get it, but you can always ask.