Cleaning the underbody won't help if water got into the ABS Module connectors and started corroding them.

The first thing you need to do is address that C101C code. You already bought the sensor, so you should replace it. You should also disconnect and clean the terminals on the ABS module since that can also cause the problem.

After that's done, the U0415 code should also go away... if not you may need a new TCM (but that's up under the dash so i dont see that being the problem unless your interior was submerged).

Edit: if you let it go too long you may find yourself replacing the ABS module instead of $5 worth of terminal cleaner and dielectric grease.