I think you will find the DB7 has unique codes and cannot be read by generic scanners. My 2006 DB7 has had a series of error codes which cannot be read. The local Aston agents system has also died, and they are waiting for an all new genuine Aston reader which will cover all recent Astons, including the DB7. This is due some time in 2011. Luckily my car has remained mobile with all vitals staying normal. The error codes are a mystery.
Don't be surprised if your engine management light just goes out in time ...
Try Snap on Solus pro v10.2
Select a Ford Mondeo gasoline variant from 2002 & use appropriate electronic key.
Failing this, this unit has a generic EOBD2 function for use with appropriate
16 pin connector.