The OEM hitch part numbers for the Pilot and for the Passport are different, so something must be different.
Also, on the etrailer dot com web site, the part numbers don't match either. The Passport accepts Curt #c13421 and Drawtite #756290 compared to the 2018 Pilot that accepts Curt #c13146 and Drawtite #75225
About the trailer harness:
The aftermarket trailer light harness is $34 and takes 45 minutes to install, compared to the OEM harness that takes half a day to install and is $$$.
The etrailer wiring
$34 harness install is very, very easy, if you have one of these tools:
mirror, otherwise you need to take the side panel off, when you really don't need to.
Just remove the easy accessible plastic parts, which have to come out if you have a flat tire, without removing the spare tire, the sub woofer, nor the driver's side rear side panel.
Here how:
1. Remove all of the things that are in the way of the spare tire, but don't remove the tire nor the sub woofer.
2. Remove the extra large plastic storage tub/s that are usually hidden and are to the rear of the spare tire.
3. There is a cubby storage hole, on the driver's side (approx 6" x 6" x 6'), at the very rear and it needs to come out, so you can slid the mirror in. This cubby just pops out, with some effort and it has to come out. With the above extra large storage tub/s out of the way you can wiggle and remove the cubby.
4. On the Passport, there is only one large white connector that is not plugged in to anything, but it has been taped to the side of another cable. You can see it with the mirror.
5. Either peel or cut the tape and free the connector.
6. The connector has about 16" so slack and can be pushed under the side panel.
7. Screw the etrailer adapter's ground wire to any chassis screw or bolt.
8. Plug the etrailer light adapter in to the Passport large connector, from step 4 above.
9. Put all the plastic back, to hide the spare tire.
10 Open the hood and install the 30 amp double extra large fuse, which comes with the etrailer adapter, in to the fuse holder. The fuse holder's lid is labeled and there is only one place for this extra large fuse to fit. The fuse panel is at the center/top of the firewall and is about 10" x 3".