Actron CP9135 AutoScanner Diagnostic Code Scanner with On Screen Definitions for OBDII (Post-1996) Vehicles - list price $179.99.
Today at Amazon.com - $60.99
http://www.amazon.com/Actron-CP9135-AutoScanner-Diagnostic-Definitions/dp/B00009RAX7/ref=pe_23330_8435640_as_img_1/
This scanner will give codes, incl. Pcodes. You'll need a workshop manual or Bentley to decipher them, but it will pull them. I use this scanner for a couple years (I paid more than $60 for it) and it works well.
Will also reset CEL and many codes (but not all on a Porsche)
Handy tool to have on hand to help decide whether or not you need
Professional help... lol