Hmmm... it could be the tire pressure but it would be accompanied by the light in the gauge cluster. Also, when it's working properly it should only go on during the first few minutes of driving, last about 30 seconds and then stop.Adobo said:Low tire pressure, maybe? (TPMS)
If you bought your truck used it's likely that something electronic is somewhere inside the seats.
Be sure to let us know when you figure out what it is