How do you access the trouble codes on a 1999 Volkswagen Passat?
There is a diag port on the panel below the steering column. Any OBDII reader can get the generic codes, but the special VW codes can only be read with a VAS5052 or VAG-COM software.
You have 2 air codes on a Volkswagen Passat can you fix it your self or do take it to your mechanic?
If you are referring to the diagnostic trouble codes (DTC), you can go to your public library and check out a Haynes or Chilton's Repair Manual for your vehicle. Chapter 6 in either book will have instructions on how to retrieve the codes, what the codes mean, and how to fix/repair/replace the component(s).