The service engine light went on a couple of days ago on my 2002 Expy, 5.4. There is no visible or noticeable problems with driving. The autozone guy found two error codes P0174 & P0171. Does anyone have any thoughts on where I can start to resolve this issue? Thanks

 

Follow the PCV hose around the back of the engine and inspect the rubber elbow at the intake port.

 

The black composite that covers the tube is pretty much rotted away. The elbow is in place although the black composite stuff is in bad shape.

 

You have to remove it to inspect it properly. Sometimes the interior is collapsed or plugged, and sometimes the cracks in the outer surface leak vacuum.

 

. I found no cracks or issues that might cause a vacuum leak. Purchased some MAF sensor cleaner from Auto zone...followed directions and that cleared the the service engine issue.