i know its been a month since you posted but thought i'd throw in some info in case you're still stumped.
F5 indicates a fault in the drive system (we already know this)
the possible causes listed for that code are:
-Faulty: wire connections @ T1D, T2D, or (T3D if equipped).
-Failed: current limit set too low, failed D5D or D4D.
-Failed: driver board or failed logics

I would test the drive transistors and all the diodes and make sure none are blown.
the drive transistors are known to cause issues like this so i'd test them first.