I’m kind of leaning towards a dealer installed disabler unit like shadowfax mentioned but I thought most of the time these were stashed out of sight.
That brings up even more questions though. Why would a dealer leave it in place, etc?
You might try dropping by a couple of BHPH (buy here, pay here) car lots and ask them. You’ve probably seen the ads and signs; good, bad, no credit, we finance, weekly payments, etc, etc.
Some BHPH lots use disablers and should be able to tell you in a second if that’s what it is or not. Even a lot that does not use them is probably familiar with them.
Just curious of course, but how long ago did you buy this car? You did get a clean title with no liens, etc didn’t you? People have been known to sell cars before with money still owed on it.