I bought a code reader a couple of years back. We were stranded in a small town with my Wife's Chrysler Town & Country, the transmission was in limp mode so we bought a code reader to reset it every so often to make it home.
Turned out to be a bad speed sensor and was fixed no charge out of warranty thanks to Keystone Chrysler.
Since then the code reader has come in handy several times for me, my neighbors, and co-workers. It's certainly paid for itself in diagnostic fees and probably paid for itself in free beers and meals via sharing.
I would not hesitate to buy one, they work on just about every vehicle made in the last 10 years. Shop around, some read codes out on screen in full text, others display a numerical code you have to look up in a book.