I assume you mean F87?
this is the reverse transmission solenoid error code
there is a service bulletin out on this code
has to do with incorrect voltages to the solenoid

check the voltages
should be battery volts
-white wire B+
-yellow wire B+
-green wire B-

the coils should ohm out between 4-6ohms

this problem could be a bad solenoid
a bad F&R switch
bad wiring in the F&R circuit , ie: a broken wire or bad connection at a connector.