What happens when Check engine light comes on after driving through water?

Answer 1

If you have driven through water and the check engine light in your vehicle comes on, you should take your car to your mechanic. You will want to have your vehicle checked for any damage caused by the water.

Probably will find that the ignition (plugs, wires, etc) got wet and triggered a misfire code (P0300). Allow the system to dry thoroughly and when the system detects there is no misfire after a few drive cycles the check engine light will go out.