1992 A/T
I just replaced solenoid #1. I added Costal Dex/Merc ATF and now the A/T Fluid Temp light comes on. After a few miles of driving on the highway.

Other info:
I just go the 4Runner, the pervious also had the pan dropped so the oil pan gasket is in good condition and I did not replace it. No metal or other junk in the oil pan. I've been getting code 63 some times so I many need to change solenoid #2. It sometimes does not shift properly in a higher gear. The speed sensor also needs to be replaced. I've head that slipping can raise the AFT temp but I'm not sure what that sound / feels like.

As I will be changing solenoid #2 I'll be adding new ATF. I've header good things about AMSOIL or Valvoline max life Dex/Merc. If that doesn't work I'll add a B&M A/T cooler.

Any other ideas?

 

Ok I feel like an idiot. Fluid was low.

 

Add a bottle of lubeguard.I also added a large external cooler for my 4runner.I was getting the light to come on 90 degree plus days in stop and go traffic.No problem now.
http://www.lubegard.com/~/C-112/LUBE...c+Transmission

 

Well after adding fluid. After driving around for about 15 mintes I notice that I'll get code 42. Soon after the engine will slip giving me code 63 then the A/T Fluid Temp light comes on.