Programmable, see 31.38 Load feedback fault.

Selected motor, no load speed feedback is received. See also
73A1.
Check the auxiliary code (format XXYY ZZZZ).
XX specifies the location of the speed feedback device. Either an
encoder interface module or the control board.
01: Encoder interface module 1, see parameters 91.11 and 91.12.
02: Encoder interface module 2, see parameters 91.13 and 91.14.
03: Control board, see group 94 OnBoard speed feedback
configuration.
YY specifies the speed feedback device.
01: Encoder 1, see group 92 Encoder 1 configuration.
02: Encoder 2, see group 93 Encoder 2 configuration.
03: OnBoard encoder, see group 94 OnBoard speed feedback
configuration.
04: Tacho, see group 94 OnBoard speed feedback configuration.
ZZZZ indicates the problem.