What does code p0001 mean on 1999 VW jetta?

Answer 1

Code P0001 is "Fuel Volume Regulator Control Circuit/Open."

This code is not very common, and likely to be intermittent. You could try to clear the code and see if it returns. Try checking it with another diagnostic tool, just to be sure. If the code comes back after you clear it, check the wiring and connectors related to the fuel volume regulator for any cut wires, corrosion, etc. You may have to take the car into a mechanic familiar with working on VWs to solve this, if you can't find any obvious problems yourself.