code P2770 Torque Converter cluch Solenoid circuit high

[Hieuallstar]

Hi. I just bought a Lexus 2013 ES350. It is about 130k miles. the transmission had a delay between 2 and 3, no error code. A mechanic suggested me to total flush the transmission. It looked like transmission fluid never changed before. After flush, the problem seem little better. After a long trip 500 miles, the delay was gone. Suddenly the car slipped when I tried to speed up to pass. It throw an error code P2770. It disappeared after that. It come on and off couple times and stay on now. The car still run fine, very smoothly without slip or delay now. The shop that flushed the transmission told me to replace the whole valve body. the other 2 shops told me to replacing the whole transmissions without test any. What do you think and what test should I take to pin point the problem?

[RX400h]

Here's a thorough explanation of the code, as well as typical troubleshooting steps:
P2770 Torque Converter Clutch Circuit High (obd-codes.com)

Have you thought of having a diagnosis by a Toyota or Lexus mechanic?  

 

[Hieuallstar]

Yes I would like to have a diagnostic but do not know a good honest mechanic. I try to do it myself first with my bi-direction scan tool.