Automatic Transmission in limp mode

I have a 2000 CLK-320 with 150k miles.  One day it went into "limp mode". I put my scanner on it and got p0715.  I checked the transmission fluid level and it was ok.  I replaced the 13 pin connector adapter plug and O rings.  Still got p0715.  I replaced the automatic transmission conductor plate.  I still get p0715.  What should I do next? 


Is it possible that it is fixed, but my scanner won't clear the code, releasing the car from "limp mode"?