Transmission Limp Home Mode

Here is part of some of what I have read at numerous sites but no where does it say wich sensor it might be or if the sensors are similar like with relays reading different pressures at different locations in the bod of the transmission... "There may also have been mistaken impressions of failure due to the "limp home" feature. When the computer sensed a problem, such as a sensor giving an inappropriate reading, a code would be stored in the car's computer and the transmission would be kept to the first two gears, so that owners could drive but would still return to a dealer for repairs. This could have caused perceptions of failure and premature replacement"...... Just leads me to believe that it is a more simple issue it only happens after I have driven a long distance and the tranny has been under load for a time and will reset if I shut it down and restart but still happens afterwards so before it does damage was wanting to fix ???? with out being charged hundreds of dollars to say we will rebuild it for hundreds more......