well..it actually didnt cost me a thing...and i as well thought it was the speed sensor...i took it to the dealer and they told me it was the transmission cooler line/hose and speed sensor, so i just asked the to recalibrate the transmission computer which is just fancy for deleting the code that was faulty....i left the car there for 4 days, and when i got it back..the limp home mode was gone...it was a miracle..they wanted to charge me almost 1000 bucks for parts and labor......
250 for sensors( because they are assembled unto valve body)
283 for tranny cooler lines
almost 400 for labor

By the way only the dealer (as far as i know) has the ODB III scanner to adjust this problem....

so it could be a computer malfunction ( simple and easy fix) or a circuit or sensor that went wrong....

I hope this helps