See the manual below for Bosch servicing. 

SERVICE TIPS:

E6 On the 20 seer models are most of the time a bad fan driver in the fan motor: The fan driver is inside of the motor and there is no real way of testing. But when E6 produced, its becasue of this fan driver. 15 seer models on the other hand have this fan driver built in to the board. Then those cases (which this article is not for) is a bad board.