Limp mode only after reverse

So, my car only goes to limp mode after going in reverse to back up then after I shift back to drive it will go into limp mode almost every time. I have to cut the car off then back on again to get out of limp mode. As long as I do not go in reverse, it will never go into limp mode, only after reverse. This has to be a simple problem! I just cannot figure it out! Does the PCM need to be retrained? Is there a backup sensor that messes with the other sensors and put it in limp mode? Is it the natural safety switch? I have changed the fluid and filter. I have changed both input and output speed sensors. I have also changed the shift solenoid. Please help!