Check engine light

I have a 2003 Audi A4 1.8t, the check engine light came on for the first time today after a couple hour drive. The code reads P0170 System too lean (bank one). Any ideas what this might be?

start looking for vacuum leaks, and try replacing the fuel filter.  can you watch the sensors on that scanner?  check to make sure the O2 on that side is working correctly..