2003 Audi A4 B6 Quattro Died while driving and wont start

So I bought a used 2003 B6 to Modify and use as my daily driver in the
mountains, The day i purchased the vehicle it ran fine the entire day but that
night the vehicle just died while driving down the highway. It felt like it ran out
of fuel but i just filled it up. I have ran codes on it Twice, the first time
showing nothing and then a second time after unhooking the battery and
hooking it back up and i got the code P0638. None of my fuses are blown
and the throttle body works fine when the car attempts to start.

It still turns over and tries to start but nothing.