I have 1995 deville 4.9l with 71k miles on it (4T60-E transmission). Problem is that my tranny seems to work perfect, but SES light comes on when 55mph or over and when engine is hot. I've replaced TCC solenoid but the light still comes on.
SO WHAT TO DO?????????????

drive it ....bout all you can do unless you want to replace the torque converter ...and freshen the tranny....

the torque convter just isnt locking up as fast as the computer would like it to ....things looen up and wear out over time , the line pressure probably isnt what it used to be and the lockup clutch in the converter is probably worn ...

in the end i did use a B&M shift improver on it , this tricked the mod valve into thinking into tkaeing longer to lockup the solenoid , the computer i guess saw this and allowed this to happen and not trigger the po39 code

There's a lot of information in the Cadillac forums archives on the code 39. Try searching using the search feature in the forum tool bar. Search for things like "VCC" or "TCC" or "viscous converter clutch" or "torque converter clutch" and read the posts for more information on the situation.

Have you checked the electrical circuit to the transmission for the VCC? The transmission is fed 12 volts through the brake inlock switch. The 12 volts goes to the solenoid and then back out of the transmission connector to the PCM. The PCM controls the VCC apply by pulling the circuit to ground. If the brake switch isn't adjusted correctly (or disconnected or the switch is broken) the 12 volts to the transmission is interrupted and that could be the problem. It needs a thorough electrical diagnosing before deciding to give up or replace the torque converter or rebuild the tranny.