Fail-Safe signal module (SM) diagnostics 
  6.2 Fault diagnostics 
S7-1200 Functional Safety Manual 
Manual, 02/2015, A5E03470344-AA 
127 
0x0302  Discrepancy fail-
ure, 
channel state 1/0 
SM 1226 F-DI 
16 x 24 VDC 
External discrepancy 
failure: Channel state 
1/0 with 1oo2 equiva-
• 
•  Sensor mechan-
ical activation or 
alignment out of 
tolerance 
aligned to be activated 
together. 
0x0303  Discrepancy fail-
ure, 
channel state 1/1 
SM 1226 F-DI 
16 x 24 VDC 
External discrepancy 
failure: Channel state 
1/1 with 1oo2 non-
equivalent configura-
0x0306  Internal sensor 
supply 
short-circuit 
to P 
SM 1226 F-DI 
16 x 24 VDC 
SM provided sensor 
supply voltage short-
ed to P 
Sensor supply 
shorted to P 
•  Eliminate the short-
circuit. 
•  Once the fault is 
eliminated, the power 
must 
be switched off and on. 
Short-circuit test 
duration configured 
Increase short-circuit test 
duration. 
Replace the fail-safe SM. 
0x0307  Overload or inter-
nal sensor supply 
shorted to ground 
SM 1226 F-DI 
16 x 24 VDC 
Internal sensor sup-
ply 
voltage shorted to M, 
ground, or excessive 
load on sensor sup-
ply 
Short-circuit 
•  Eliminate the short-
circuit. 
•  Once the fault has been 
eliminated, the power 
must 
be switched off and on. 
Excessive load on 
Reduce load on sensor 
Replace the fail-safe SM. 
0x030B  Channel failure 
acknowledgement 
All  Channel configured 
for manual acknowl-
edgement is ready to 
Manual acknowl-
edgement required 
Manually acknowledge 
correction of channel fault 
so that reintegration can 
0x0311  Frequency too 
high 
SM 1226 F-DQ 
4 x 24 VDC 
SM 1226 F-DQ 
2 x Relay 
Switching frequency 
exceeded; readback 
not in time 
Process value from 
safety program 
changing too rapidly 
for SM to follow 
•  Change Safety program 
logic to guarantee more 
time between output 
changes. 
0x0312  Undertemperature  All 
•  Under- 
temperature at 
microcomputers 
•  Under- 
temperature at 
I/O 
Shutdown due to 
violation of low 
temperature limit 
value in the SM 
case 
•  Check the ambient 
temperature. 
•  Once the fault 
has been eliminated, 
the 
power must be 
switched off 
and on.