Terrain management light flashes on and off?

My terrain management light will flash on and off sometimes when I let off the gas pedal and let it coast rather than putting on the brake but also can happen when braking and just bring as well typically when it happens something under the car makes a noise and if I let off Gass pedal if I am just driving or if I give it gas when I don't have my foot on the brake or gas it stops. Sounds like something scraping only when this occurs. I have taken it to AutoZone and had it scanned and nothing comes back. Any ideas?