Since he is using a Snap On, I would like to think that it is capable of retrieving OEM and generic OBD-II codes. A couple of other guesses then, maybe it had a bad connection, or maybe he didn't specify the proper VIN if he had to enter it in. Since the light came back on, something is faulty that is setting it. Ask him to read them again, being sure to set the scanner properly. If it still comes back as no codes, don't let him clear the light! Ask him if he'll reimburse you if you pay to have another shop pull the codes and they are able to retrieve the code. If he will reimburse you, go back to him for the work once you know the code. If he won't consider letting the shop that does pull the code do the work and avoid the previous mechanic. Another thought is try Autozone. Some people here (I've forgotten their name again) have gotten Autozone to read the codes for no charge under the assumption that they would purchase whatever part it needed from them.
