I purchased a low-end OBD-II reader from Wal-Mart a few months ago. Now I'm in the market to purchase a used car and I was wondering how useful the reader will be when I go to look at the vehicle. Of course I plan to test drive the vehicle but I was looking for a more rigorous way of evaluating the vehicle before I take it to a professional mechanic for a pre-purchase inspection.
How helpful will that OBD-II reader be to me prior to taking the car to a professional mechanic? If no DTC codes show up on the reader, does that mean nothing is likely to be wrong with the drivability of the car?