I have a 2005 Nissan Sentra (base model, FWD, 1.8L 4-cyl engine) and I took some bad advice from the Maps app on my iPhone and I ended up driving on a very, very bad road. At one point, I drove into a puddle that was quite deep where the car got stuck with the front end partially submerged - I imagine the water level was probably more or less at wheel well height towards the front right.
I managed to get out by putting the car in reverse, then drive, etc until I was free. During the final reverse attempt I was giving the car a bit of gas and, though the front wheels were mostly slipping, I slowly crawled back up to safety. It was during this final attempt that the engine light came on in the car. The engine itself works though, and I drove about 100 miles or so after this without incident.
However, there's a new sound in the engine that's faint, but audible, especially at higher RPM. When I opened up my hood I noticed that the entire engine area was dirty, presumably from the mud water that was splashed up during my attempt to escape. I don't have a lot of money, so I guess what I'm wondering is:
What may have caused the check engine light to come on? In the 1.5 years I've owned the car it's never come on before.
For each possibility, what is the danger in continuing to drive the vehicle without taking it to be serviced?
Is it safe to hose down the engine area to get rid of the dirt?