Does the light look like a tire with an exclamation point in the middle? If so it is your tire pressure light. That vehicle is equiped with Tire Pressure Monitoring System(TPMS). If that light is on it is indicating that the sensors are detecting a low tire pressure. It will trigger usually at about 30 PSI. So try setting the tire pressure(about 35psi for your truck) and drive it for a while. The light should go back out.