Hi guys´n girls!

Once again I need your help with a little new project.
I own a ´93 Blazer S10, 262cui, 4speed automatic transmission and I would like to install a LED on the dashboard that lights up during the converter clutch is active.
So what now? I need a signal at first and I guess, I can find ist somewhere on the electrical connection between PCM an transmission.
But where?
I have an electrical plan of this section in my Haynes repair manual, but the cables are named with the shorts TEMP IN, MODE C, MODE B. MODE A, TCC, CTRL OUT, A OUT, B OUT, MTR LO, MTR HI, and TCC again.
So what? Is there anyone here to give me a clou?

Thanks from Austria!