I had the same problem with my 92 SC400. Finally decided to tke to dealer, but gave following one last shot.
Pulled fuse for Trac, left it out for a week. Drove the car as normal, TRAC light on all of the time. Put fuse back in, no light, drove abot a mile light came back on. Next day while driving I noticed the light was NOT on, that was about a month ago. Light is still not on.
I know the 'system' is working because,
The light blinks when I lose traction, just as the manual says. I have seen it blink/flash when going over slippery railroad crossing, and other such things.
Worth a shot