What's this hose coming from the air filter box?
 

Just was looking in my 2000 4.4 engine bay to see where the air filter box is because it's time to change the filter, and I noticed that there is a smaller hose also coming out of the top part of the box, at a right angle from the big hose going to the engine intake. This smaller hose points to the front of the car and then goes down to connect something below the filter box that I'm not sure what it is. Anyway I noticed on my 4.4 this hose is not connected properly - looks like it has come loose. Anyone know what this hose is and what it connects to down there?

It's crankcase ventilation. Gasses from the internal engine are routed through the air filter to be burned and catalytic converted for clean emissions. The disconnected hose didn't hurt anything but you should reconnect it to keep your emissions system intact. On mine, there's a slip ring clamp that locks it back in place. Lift the ring to unclamp, press down to lock.

Thanks, will do.

My engine light came on. OBD II code P1174. I found this hose unattached from the lower housing. I hope this is what triggered the engine light.

Don't count on it!