I doubt your transmission needs a flush. Not alot of "crud" will get into your transmission, just the oil in it seems to lose it's "lubeness" lol. Your shift solenoid is probably bad. Easy to fix? I dont know. Usually if one code comes up, a few more pop up along with it because other sensors are getting a bad reading r low performance due to another part. Check a chiltons or haynes manual for replacement of the shift solenoid. Im not sure if it's in the actual transmission or external. Could be an easy fix, could be costly.Also, low transmission fluid can cause an electronic transmission to either not shift or a long hesitation.
Previously Known as Absinth