The lock-out indicator light in my 94' Dodge Cummins Diesel 2500 Ram pickup stays on and the transmission will not shift into overdrive. I have tried disconnecting the speed indicator and checked and cleaned all the electrical contacts. If I disconnect the lockout switch it still won't shift into overdrive. As soon as I reconnect the lockout switch the light indicator is always on. Is there anyway I can elliminate lockout completely as I never use it anyway? Do you think it is a TCM problem or the solenoid? Does the solenoid shift the transmission into overdrive or out of overdrive when activated? Where can I find a schematic or solenoid (and transmission) service information? The Haynes Repair Manual chooses not to supply anything but a bare minimum amount of info on the automatic transmission

I Have the same issue with mine. Sometimes it will go off and the truck will shift into overdrive but most of the time it won't. Don't know if it is the switch or solenoid or something else. Also when I first start it up, sometimes the button is off but it goes on when I shift into gear. Im going to put a new button in and see what that does. I don't think that's the problem but it's the cheapest and easiest place to start.