Can there be still something wrong with my ABS if the light is NOT on?

I have a 2006 Honda Element which I am selling. An interested party took it to a mechanic to look over. The mechanic said the ABS was returning "abnormal" codes and the repair would cost $500. I was surprised by this bc the car drives great and the ABS light is NOT on. I called the Honda dealership and they said if there was something wrong with the ABS, the light would be on. They said they could not even get codes unless the light was on. Could you weigh in on this? Thanks in advance.

unless the bulb burned out... also yes would have abs codes if not functioning properly, also if it doesnt work if you slam on the brakes the front wheels will lock up. Sounds like they are just trying to lowball you