absence of trouble codes
 

Greetings; I'm going to try my best to describe wut is going on with my '99 s10 blazer 4x4 ( so please bare with me).
since I got the rig , there has been several times in which it has had a problem or issue, ( misfire, broken speed sensor, not running good at all going up hill , etc. So while trying to get things fixed, I plug in my OBD2 code reader in, & guess what!: no stored codes, no recent codes, nothing.
not only has ther never been any trouble codes, the S.E.S. light has nvr came on to notify me of a problem. & the S.E.S. light does work, it lights up when I turn the key to start the engine.
I don't know if it matters, but, when I was driving my '98 s10 blazer 4x4, that S.E.S. light would light up when there was issues with emissions, transmission trouble, etc.
so my question is this: why isn't my S.E.S. light lighting up to inform me of a problem?

Does the SES light work with the key on/engine off?

Yes, after turning the ignition to on ( not to start) it stays on until after I start the rig

Then it is working. Certain conditions have to be met in order for a specific code to set, but usually failure to come on is never a problem! Especially with a misfire. If you have concerns regarding failure to set specific codes you can review the documentation in the OBD2 codes portion of the Tech Section to find out what triggers the particular code to set and turn on the SES light. Hope that helps.

enhanced trouble codes
 

So after being able to access the enhanced GM codes in this '99 s10 blazer 4x4, it came up with 5 codes:
P0605:control module programming
U1026: loss of class 2 communication with ATC
U1042: Lost communications with brake/ traction control system
U1192: loss of passlock/ EVO class 2 communication
U1193loss of VIM class 2 communications.

Now, could someone please explain what these mean?
thank you ahead of time for all your help.

Codes list
 

There is list of codes at this site. All of those communication codes should clear if you fix the P code. Sounds like you have a bad communications module. Maybe the computer needs to be reflashed??