A BS Light.
When I took my car into Midas to have it looked at, yes, I knew they said they couldn't diagnose why my "ABS" light was on. But when they diagnosed the problem with the brakes, I assumed, and assumed wrong, that once they fixed the master cylinder, that the light would go off.
"We don't know why that's on." said the repairman.
"Take it to a dealer to have them check the computer." said another.
So, $311 later, my ABS light is still on, and my birthday trip is still off, and I'm still might discouraged.