I’m no expert at all on the DB7, but while I was crawling around on the Internet I came across the official OBDII Diagnostic Manual for the DB7. This is the pre-Ford era of Aston, and all the stuff for the Gaydon era cars might be similar, but not the exact same. All cars sold in the USA after 1996 had to be fitted with an OBDII port, so its no suprise this manual is from 1996. If you are a DB7 owner out there, then this might help you.
Aston Martin DB7 Diagnostic Manual
Here is the official Aston Martin DB7 OBDII Diagnostic Manual from May 1996. I found it posted by someone on the Internet. They obviously had a printed copy and scanned it (there are even a few spots where you can see a note).
The official place to get the P codes explained is on the Aston Martin Technical Information Website (which I have covered in another blog post). What I dislike about the format on the website is that the codes aren’t in a single document anymore, but rather each has its own web page section. This makes a lot of sense for Aston Martin (alleviates the need to keep a large complicated document up to date), but for us DIY repair guys without an expensive $2,600 annual subscription to the website it’s a handicap. So, I would recommend that if you find the P code you are experiencing in the list below just check out the PDF. If the P code you have isn’t listed, perhaps spend the $100 for a one day subscription to the website and look up the code you have (and maybe send me the details or your code and a PDF print of what was on the website about it). Or succumb, and take your car into the dealership.