transmishion fill cap where

If the dipstick goes into a large hole (about 1" diameter), the fill is the same as the dipstick hole. If the dipstick has a short tube it goes in, there's a large bolt on the top of the transmission that you have to remove. Either case, the hole is essentially the same (one just has threads on it for the bolt) and you will need a funnel with long extension (or hose, or other way of getting the fluid in the hole) or you will have a mess on your hands.

not actually always true especially with these vehicles.... the fact that the Passport is even in the Honda section is a joke.... it's an ISUZU with Honda badges.... not one part on it's Honda other than the logo's.... now this will make you even more crazy.... that truck has a General Motors 4l30e auto tranny in it.... those tranny's DON'T HAVE DIPSTICKS!!!! they're sealed because apparently GM didn't think you would EVER need to change/add/check the fluid level for the entire life of the tranny (which considering how weak they are probably isn't really too far off)..... so you'll need to get after the fill plug it's on the right hand side (passenger) side of the tranny and the head for the bolt is 22mm IIRC.... if you crack it open and on level ground it immediatley starts dripping tranny fluid before you even get it all the way out.... you're good to go.... if not then you'll need to add tranny fluid until it does run out of said hole..... you can buy a little hose that screws onto the bottle of ATF that you can run up to the fill hole so all you have to do is squeeze the bottle to fill it....

Is the fill plug on the pan or on the tranny case?

its already been said, passport is an isuzu with a honda badge. theres 2 plugs under the trans. put the passport in park; let it run for 5 mins.; put it in nuetral with the Ebrake on; raise the suv up; loosen the plug that sets up higher than the 2; if nothing is comin out then put trans fluid in it until it drips out. then your done