Well that's smar of you. I suspect that your son's REAL problem is that his appetite is bigger than his wallet---probably he's looking to buy a brand new car rather than a good used one?
I'd say, yeah sure, his age is against him, as well as his score, but maybe also the amount of money he's trying to borrow.
If he has to drive something old for a few years until he builds up better credit, well that's what he has to do then. Money's tight right now for people with his demographic and score.
I also hope he doesn't bite on some high interest loan offer from a dealer "mouse house" (dealer's own financing).