My car is showing a code for D Solenoid and wont go into 5th Gear, what could cause this issue? Shift Solenoid, Automatic Transmission Control?

[avoshell1209]

I have a 2008 Lexus GS350 AWD, for some reason the check engine light and he VSC light came on.  I took it to a shop and they told me that the cold is reading D solenoid.  I cleared the code, and the VSC light went off as well as the check engine light, but came back on after about 5 minutes.  I'm being told that it could be the shift solenoid, but other people are telling me that it could just be the automatic transmission control.  The shop recommended me getting a new transmission, but I'm not trying to shell out 4k for something that could only cost me less than a grand to fix.  Any help would be greatly appreciated. 

[RX400h]

What is the code reading? There is lots of information out there about codes and repair costs.
How many miles are on your odometer and what is the driving mix of city and highway?

 

[Bykfixer]

https://mechanicbase.com/transmission/shift-solenoid/
this might help ease the grief. 

[RX400h]

Quote

Many shift solenoid-related codes can be solved by doing a transmission fluid replacement or carrying out a transmission flush. A transmission fluid change is often not that expensive and worth doing.

Perhaps a good first move.