Got into the Pathfinder yesterday and it smelled damp with mildew. This is the second time I have noticed this. The first was before I took the truck to Nissan for repair. The second is now after I got it back and it's rained a lot lately. The water puddle is found underneath the second row back seat on driver side. When I pulled up the seat cushion and unlatched the back seat, if looking onto the floor towards the backseat door, you will see a puddle in the area the backseat latches onto. The truck has a sunroof and all windows have been closed. Where do you think this could be coming in from?

Sounds like your left rear sunroof drain is clogged, although depending on how your truck sits and the incline/decline of your parking space, it could also be the front drain. You can check it by opening the sunroof, you'll see two parallel channels on each side. The inboard channel is the sunroof track, the outboard is the drain channel. Pour water into the drain channel on a downhill and you should see it come out the front hose behind the front wheel, do the same on an uphill and you should see it come out around the rear wheel. R51's never have many drain problems and I frankly can't recall if the rear drains egress in front of the rear wheels or behind. The right way to clean out any drain is from the bottom up, because except for the occasional kinked hose, clogs are almost always in the egress fitting and not the hose. So get at the egress fitting, pull the hose off it, put a shop rag over the top end of the sunroof channel to catch debris, then blow the hose clear. Then stick a screwdriver through the fitting, that's usually where you'll find the clog. The rear fittings will probably take some work to access, it usually requires removing (or at least loosening) the luggage room trim. However, it's worth the effort. Simply blowing or snaking the drain from the top is almost always a temporary solution, you're likely to have the same leak all over again in a month or a year or two.

This is good info. I will look into it and post back my findings. Thanks.

Curious if the rivnuts are prone to spinning on the Pathfinder like they do on the Xterra's when it comes to the roof rack? I was able to see the drain hole in the front towards the windshield but unable to see the one towards the rear of the sunroof since it is placed under the roof rack as you mentioned? I just don't want to get stuck with a bad spinning rivnut in which the headliner needs to be pulled to get to it.

Anyone know if the rivnuts for the roof rack are prone to spinning such as the Xterra's do which in the end require the headliner to be taken out to access?