I always cover the pcm the best I can with plastic bags to protect it just in case. Although Ford helps by mounting it on the firewall away from the engine. I wouldn't use the high pressure of a car wash but the mist setting on regular hose pipe spray nozzle will work.

 

It is amazing at how much these newer trucks do collect a lot more dirt. I think a lot of that has to do with the wheel wells these days. They don't cover near as much as they used to. There is also no cover on the bottom of the engine so a lot more debris make it's way into the engine compartment!