I found out a couple of days ago that Auto Zone rents portable read-out machines that will tell you why your check engine light came on. When I say rent, they put the charge on your card, then remove the charge when you bring the machine back. The only cost is whatever interest you might accrue in an hour or overnight or however long you keep the machine.
Which machine you rent is different depending on your model and year. The readout can be cryptic, but it gives you a clue what’s going on. And if the explanation isn’t clear, you can take the error code and search online for information from other folks who have gotten that code and decided to post how they fixed it and how well it worked out.
I had no clue that this service was available. Has anyone else been pleasantly surprised lately?