Wet floor after rain

Hello,

My 2002 Sonoma (3 door extended cab) leaks when it rains. The lining beneath the rubber carpet is soaked through. It appears to be a chronic problem, some rust has formed and the wire harness gets wet. Just bought the truck used, the guy had an air freshener in it. Now I know why. Any thoughts would be appreciated. Thanks!

What part of the floor is wet?

The driver's side floorpan, from the seat mounts all the way forward to the base of the firewall. Pulling back the pad and matting reveals standing water in this area.

Maybe this will help. I had a similar problem on my 96 extended cab Sonoma (2 door). The difference was that my carpet was wet from the seat back to the rear wall, passenger side. There is a fill strip along the edge of the roofline (over the rear windows) that covers the weld that joins the wall and roof. There was a pinhole in the weld, which allowed water to drain along the B pillar moulding (inside the truck), directly onto the floor. The carpet then wicked it up and spread it around. A dab of RTV sealer fixed the problem.
To find a problem like this, you may have to spend some quality time with a garden hose.