mayanks

I own a 1998 Lexus GS400 Recently this week the check engine light stayed on full time when the car is on and sines few weeks the light kept coming and going on and off I took the car to my mechanic and when he checked the light, he told me he got the code P.0768 which indicated the shift solenoid D in the valve assembly or valve 4. The car runs fine, no stalls and I want to know how to replace the shift solenoid D and i don't know which one it is in the assembly. Which is Valve 4 or Solenoid "D"?