According to the owner's manual. Run the car. Wait until it's hot - fan kicks in. Turn off, I got 90 secs to check. 09 Ody & 10 Accord.

** I don't recall reading that in the past (old Hondas). And honestly, I don't recall this from reading my 06 Accord's manual.

- I generally don't like to check fluids while it's hot.

- My cold reading on the transfluid is just a tad below the bottom mark.

Questions:

Will there be any issues with adding "too much" trans fluid?

Oil for example, when one add too much, it could cause it to foam or bubble.

 

Adding to much transmission fluid can do one of two things that I know of. 1. Can blow a seal out from to much fluid/pressure 2. once heated, too much can over flow out the dipstick. Ive personally seen 2. happen. **** smells horrible and is worse than seafoam LoL.
On a side note, All autos I check trans fluid on, 95% have to be running in park at "operating temp". So what your owners manual is saying isnt much off from what i've always read/been taught.