I have a 1994 S10 Blazer with a 4l60e. On start up, transmission shifts through all the gears. Once I stop at a stop sign or stoplight the transmission goes into a limp mode, third gear only with a manual shift from second. No codes on tech2 scanner. With the scanner on live transmission data, and truck cold, it reads transmission temp at 206 degrees. If I unplug the harness at the transmission the temp goes to -40 degrees, then when plugged back in the temp reads normal (85 degrees). If I cycle the key off/on the transmission temp goes back to 206 degrees. Tech 2 also shows a "3-2 Control Feedback Fault". I've checked the fuses, replaced the Ignition Switch, Pressure Manifold Switch, 3-2 solenoid, even installed a new internal harness with no change. Local transmission shop couldn't help either. Any help or direction on how to test without throwing more parts at it and wasting money would be greatly appreciated.

I'd be checking the wiring from the temp sender. If the system detects high tranny temps it'* go into limp mode to keep from burning it up.

Yeah, wiring. I've seen a lot of Astros do the same thing just from damaged wiring.