Truck not shutting OFF after running in rain..

[Possmguts]

Hey guys..
2013 KW T660, CM2250, 13 speed.

After running in LOTS of rain yesterday once parked the engine wouldn't shut off with the key.
Ended up yanking the ECM fuse to shut it down. Several weird things...
The dash lights stayed on with key off, but radio and everything else powers down with key off. when I turn the key ON it doesn't go through all the clicking noises like it still had key on.. same when turned to acc.
Truck starts and runs fine though. Just have to pull ECM fuse to shut it off and it still has power like the key is on even with it in the OFF position.

Gonna rain all day again today too..

Will this clear up once it dries out? Where would I start looking for water that is causing this?

Thanks