Take an OBD II reader with you to check the vehicle codes. I have a Blue Driver and it will show when codes have been erased (most do that). It’s a highly rated unit and runs about $99 and pretty much anyone can use. This can be handy whilst negotiating.

I use my legs. If I like a car I must be willing to walk away (if only to make a threat).

Check on YouTube to this very question. There are tons of good quality vids out that are very helpful.

Almost always I take the car in question to be checked over by my mechanic. $100 is a small price to save ones self from making a big mistake.

Good luck.