The chip for starting the van is pretty immune to damage (it's probably buried under a drop of epoxy).
It's not connected to any part of the remote door lock system.
The circuitry for the remote lock system is not so well protected.
The first thing to do is open the remote's battery compartment (remove metal key ring, look in Owner's Manual and at edge of the slot the flip-key hides in... you'll see a molded drawing of the battery stack. Pop open the battery cover by pushing up on that lid (i rotate a very broad-blade screwdriver, a dining room table's spoon handle or something similar would be a suitable tool).
Remove the batteries and look for corrosion and mess.
If things look dry without a dried salt-like deposit, you may, if lucky, just be facing dead batteries
(does the "transmitting!" light illuminate when you push the button? "Yes" is good, "no" could be dead batteries)
When these things are dropped into salt water, the recommended procedure is to soak them in fresh (or distilled) water to remove the salt.
It might be a good idea to do that for your detergent-affected remote.
Flush with lots of fresh water (if you have "hard" water at home, use distilled).
Having the battery cover open helps this.
Air Dry thouroughly. (don't use a heat gun) Putting it in front of your house's warm air duct is OK.
good luck
--dick