I want to check the level of atf temp in my subaru forester 2010. On checking the transmission fluid level after the car was driven about 10 km and was put in each gear and setting the select level in the "p" do i have to turn off the engine or idle the engine before i check the atf level?

you say temp and level?

 

for level,  it doesn't really matter if you turn the engine on/off or not.  don't turn it off and if you can't read it then try turning it off and letting it set for just a minute.

 

can check it without warming it up - it'll still show and let you know it's either good or not.

in general you won't have much ATF gone unless there's some leak somewhere so it's almost certain to be fine, which a quick glance will show.  if then there's any questions then do the full warm up thing.  some have "cold" and "warm" levels on the stick - so you just use the "cold" level if checking when cold.