hi together,

there you find the info:

Status LEDs

manual

each digital SM provides a DIAG LED that indicates the status of the module:

• Green indicates that the module is operational
• Red indicates that the module is defective or non-operational

There is no indication for a solid red light. Just this. So maybe it is just an error. Try to get someone with a programming device, who can look online.

hope this helps,

regards,

Depends.

Module defective, most certainly.  However, if any of the digital outputs are functional, the module is not defective.

There are many SM 1222 module types.  Is yours a simple DC (24V) output type?  Is your 24V L+ connected to a working 24V supply?  Is your M also connected to the common leg of the same 24V DC supply?

Is it possible one digital output is shorted or wired incorrectly?

If your module diagnostics configuration has everything enabled - which you can tell from a documentation package for the PLC project (pdf or printed), or using TIA Portal, you can see what is going on.

If you are the original developer of the project and the system has a Siemens HMI, you can add a diagnostics screen to the HMI for almost no effort and then you can review the PLC diagnostics buffer to find the reason for the red LED on that SM 1222 - and no TIA Portal is required after the HMI is updated. 

MMSaifi

Hi, all...

What is the meaning of SM 1222 DC DIAG (Diagnostic) LED always RED after power UP?