You will need a Durametric, PST2 or PIWIS to read the airbag codes as they aren't ones Porsche has to release to third party maintainers and thus a normal code reader won't read them.
You didn't say what year your car was. The 986s had belt buckle problems and grounding problems. Mine went in 4 times before it was finally sorted and it took both belt buckles and the grounding strap twice. There was a TSB for the grounding issue.
http://sites.google.com/site/mikefocke2/airbagwarninglighttsb