I got accepted last month as an out of state student and SDSU is my top choice so I am 100% going to submit my intent to enroll and what not.
I have completed my 2 years of History courses required for A-G, however this year I have a D+ in my AP Economics (History Course). I am going to try to get it up to a C- with finals coming up, however if I am not able to, can they rescind me based on that one grade?
My other classes are fine and GPA should be the same if not higher than the one reported for the previous 6 semesters.
I am very worried 
There is a possibility that your admission will be rescinded since SDSU’s admissions policy states that you must earn grades of C- or higher during your senior year. However, I am sure they make exceptions, especially in your case. Since you were admitted early you are at the top of their admissions pool so I do not think a D+ in AP Econ would be an automatic death sentence. With all that being said I highly recommend you try your hardest to get that D+ to a C-. In the case that your grade stays the same, you should definitely talk with the SDSU admissions office ASAP. Make sure not to get anymore D’s and certainly no F’s.
Rather than worry, spend that energy studying AP Economics. Simple as that.
P.S. The reason that you are worried is that you mistakenly believe that the decision is in the hands of SDSU when the reality is that you control your own destiny here since you have already been accepted.
@CharlieEcho35 and @Publisher have both given you good advice so do everything in your power to get that D+ up to a passing grade. SDSU has rescinded acceptances in the past due to poor Senior year class grades, but if this is a one time occurrence they should be more understanding.
Looking at your other thread, I would say that since your GPA is on the low side for SDSU and you were accepted for being an OOS applicant vs. a top Stat applicant, make sure you other grades are not slipping also.
Best of luck and if your final grade ends up to be a D then contact SDSU admissions and see options are available.