Chapter 17 Safe Torque Off FunctionMS300 
776 
 
17-7 Error Code and Troubleshooting Instructions 
17-7-1 Error Code Description 
Refer to Pr.06-17–Pr.06-22 for the fault record; the relevant STO error codes are 72 / 76 / 77 / 78.   
The definition is described in Table 17-4 below. 
72: S1 internal circuit detection error 
77: S2 internal circuit detection error 
78: Internal circuit detection error 
S1 internal circuit 
detection error 
S1–DCM internal loop detection error 
Safe Torque Off function active 
S2 internal circuit 
detection error 
S2–DCM internal loop detection error 
Internal circuit 
detection error 
S1–DCM and S2–DCM internal loop 
detection error 
 
Table 17-4: Error code description