over drive button?
 

95 v6 4runner automatic isnt switching to over drive off or on seems like the button isnt doing anything lights up on the dash but i dont feel any coast or drag weather it would be on or off. so when i get on the freeway im running really high rpm almost feels like im not going into final drive . put a new tranny in a year ago and thats why i did it in the first place but i dont think that is the problem ....also over drive will kick on and off sometimes out of the blue usually around 50mph when it does it ive noticed ....please help!!!!!!!!!!!!!

have you cleaned the switch on the shifter? i remember reading a thread about this.

I know there is a temp sensor on the back of the lower intake manifold (3.0 3VZ) that if bad or the wire is broken connection will prevent OD.
Other possabilities are the harness going over the trans has a bad spot in it stopping the OD solenoid is not operating (A way to test this is if you have 4x4 AT (A340H) and it does go into 4WD then the OD solenoid is good since it shares)

If the dash lights up (OD) the ECT should be getting the signal if your ECU harness isnt messed up.

3.4 and A340F I would think engine temp sensor for AT again but I havent any Idea where its located.