Festo CTEU-CO Manual, Functions And Maintenance page 46

2. Diagnosis
Byte 0 Byte 1
00
20
20
20
20
00
30
00
FF
Tab. 2/7: Bus node Error Codes (as per DS401)
2-10
The pre-defined error field as fault memory
If the Emergency Message is transmitted, a compressed form
of the fault information will be saved parallel in the Pre-Defined
Error Field (Index 1003).
Device 1 + 2 DIAG, Error Code
The Pre-defined Error Field serves as fault memory for the last
faults ascertained.
Error Codes
Note
If several Emergency Messages from Tab. 2/7 are present,
only the most recently reported is transmitted to the mas-
ter controller.
Explanation
00 No error
22 Short circuit diagnostics
23 Short circuit at outputs
31 Operating voltage too low
33 Load voltage too low
50 Hardware fault
81 Node guarding or Heartbeat error
FF Configuration error
FF Diagnostic message from I-Port telegram
Festo P.BE-CTEU-CO-OP+MAINT-EN en 1101NH