Do buy here pay here lots put trackers on their cars?

Many do, and it's legal — the lot owns the car until you've paid it off, and the device is disclosed in the paperwork you sign. It's worth reading that page rather than discovering it later.

There are two different devices and people often mix them up. A GPS tracker reports where the car is, so the lot can find it if it needs to repossess. A starter interrupt is separate: it prevents the car from starting, and some lots use it as an automated late notice — miss a payment, the car doesn't start until you've paid.

The starter interrupt is the one to ask hard questions about. Ask how much warning you get before it triggers, whether it can activate while you're driving (it should never be able to), and whether there's an emergency override code. Reputable lots answer all three without hesitating.

You can ask for the device to be removed once the loan is paid off, and you should — otherwise it stays in a car you now own outright. Ask about that at signing too, so it isn't a negotiation two years later.