A SCANGAUGE 2 would be invaluable.
TFT- transmission fluid temperature- is the parameter you would be looking for.

Baring that, what temp is it supposed to be , when checking? Is it critical, like some CVT's are , due to fluid expansion?

Or are you supposed to just check it after everything is at full operating temp?

 

Check the FSM for correct temp - usually about 105F (just barely above our skin temp).

Regardless I would Measure what comes out to ensure at least that much goes in.

Also loosen the Fill bolt first to ensure you can add once drained.

The Check when at Full Temp is Only for the older school trans with traditional dipsticks.

 

Thanks for the reply. I am going to make sure I put back what I hhave drained, should be very near the correct amount.

 

Please follow the procedure correctly, it is just not a matter of putting in the same fluid that came out. WS Fluid is a thermal expanding fluid when warm, so the fluid exchange is much different than traditional ATF.

Follow this video for the correct procedure.

 

I have viewed this video several times but, when I went to use the wire to put the computer in diagnostic mode there was no pin in the upper portion of the connector. Ultimately a Scan tool for Trans temp reading would be the solution. This car is a 2020 Highlander. It has many empty slots empty in the connector.

 

Timely thread, i'm about to attempt this fluid change today. Yesterday I practiced putting the car into the transmission temp detection mode, where you move the shifter between N and D several times. In my V6 2020 Highlander, I did it without any wire jumper and it worked.

The part I'm concerned about is finding that dang transmission fluid temp bypass button thing, none of the manuals or videos show you exactly where that is located, I hope it's obvious when I remove the wheel well cover.

Edit to add: Holy cow what that process that was, especially that bypass button, accessing it to push the button in, while putting the pin in was a feat with how that thing is installed in this vehicle.

 

Timely thread, ...

The part I'm concerned about is finding that dang transmission fluid temp bypass button thing, ...

sorry for the exam but what does this fluid temp bypass button do (besides the obvious) or why is it necessary to do this step.

 

Thanks for the heads up on the temp detection working without the wire jumper. That button was bit of a bear to get at beng buried behind the wheel well cover. Going to try the temp detection mode next time I use the car. In reply to a previous post about fluid temp volume exchange, My vehicle was in a heated shop and all fluid was at the same temp, so no error in expansion.

 

I can verify using the laser gun to measure temperature as very accurate. When I did this service in my 2014 Tundra, I do have a scan tool that shows live transmission temps but also wanted to test the laser temp to see how close it was....VERY close...within a few degrees. So that's good to know, next tranny service I won't even bother with the scan tool. (Some say just replace the same amount that came out but, nope, what if it's too much or not enough? Not worth the risk with transmission prices.)
Oh, and the warnings about dropping the transmission pan in order to replace the transmission filter are true.....they DO break very easily...I had two break on me when removing....made the job a nightmare! So, now, I don't even mess with them, just do a drain and fill every 5-years or 50,000 miles, whichever comes first. (And only using Toyota transmission fluid, it's great stuff)