Faults In The External I/Os - Siemens SIMATIC S5-90U System Manual

Diagnostics and Trouble Shooting
5.5

Faults in the External I/Os

Fault
Module with
No
fault LED
(red) ?
Yes
No
Is red LED lit?
Yes
Module power
No
supply ok?
Yes
No
Short-circuit at the
outputs?
Yes
Eliminate short-
circuit
Figure 5-5. Analyzing the Cause of a Fault in the External I/Os
5-12
Power
No
supply ok?
Yes
Is module
No
addressable via
PII, PIQ (STATUS
VAR, FORCE
VAR) ?
Yes
- Check (replace)
module
- Check program
Check supply
leads
No
Defective fuse?
Yes
Replace
fuse
Bus
No
connection
ok?
Yes
Replace mod.
Check connections of
No
by simulator mod.
Check with STATUS
VAR and FORCE VAR
possible?
Yes
Replaced module is
defective
EWA 4NEB 812 6115-02b
S5-90U/S5-95U
Check
supply leads
Replace
bus unit
other bus units and
interface modules
Defective module