I have techstream, so troubleshooting the solenoids was easier. TS allows you to individually activate each solenoid to see if they are working properly and allows you to activate it back to back to back to try and pass particulates through it if they are slightly clogged. I troubleshot my solenoids and actuated each multiple times, which seemed to help with issues for a while. When codes popped up again I replaced the solenoids that has issues with Toyota parts, which I found by going through threads and parts diagrams. I'll look through my notebook and see if I still have part# = solenoid s1 etc... all of these are on the outside of the valvebody and are easily accessible if you drop the pan, but are expensive @ $100+ each. Filling the transmission pan back up via techstream or the paperclip in pins 4 and 13 method is the most time consuming part of solenoid replacement.
Even after replacing solenoids the codes came back sporadically. So I decided I'd try the Sonnax part and see if that fixed my issue after reading through the beginning of this thread. I reached out to Sonnax to ensure I was getting the correct part number and where to get it. Their suggestion was rockauto but the were also sellers on eBay.
For transmission fluid I used Idemitsu Automatic Transmission Fluid type TLS-LV, 12pk - ATF Oil Auto Transmission Fluid, Compatible with Toyota, Lexus, Scion
https://a.co/d/ifY31VW since it was the cheapest way I could find anywhere and after some research it looks like Idemitsu manufacturer the WS fluid for Toyota.
When installing the Sonnax plug the valve body has to be removed and disassembled. This is scary the first time stepping into it blind because the is next to zero information on the 6 speed transmission in the GX460. Luckily there is some information on the LS460, the tundra, and the 4 runner with the 6 speeds, which all seem to have the same issues to different degrees. So I tried to take as detailed pictures as I could to help out the next poor guy laying on his concrete floor at 10pm trying to figure out where the balls are all supposed to go.
The costs of the job...
-Transfer pump $10 - I use a cheap 12v fuel pump from Amazon and a Milwaukee 18v battery to pump all of my new clean oil.
-Oil $70-130 depending on where you get it. You'll need about 1.5 gallons each time you pull the pan.
-Solenoids are north of $100 each for some and others are cheaper. I think I spent $500-600 on solenoids to replace them all.
-Sonnax kit $37 shipped
-Time, on my back under the truck, about 4-6 hours steady with a big chuck of that being refilling the transmission by Toyota procedure.
If I was taking this to a shop to do just the Sonnax plug I would expect $200-300 in parts and another $600-800 labor. If I you do all the solenoids too I'd add another $700-800 in parts.
