I just looked at an instrument wiring diagram to make sure that your car doesn't have a transmission over heat light. Does the light on your dash look look a red oil can? If so it is a low oil pressure light and illuminated when your truck's engine has less than 3 to 6 psi oil pressure at which stage you can do serious damage. Check the engine oil level and top up if required. The LTD model has both an oil pressure gauge and an low oil pressure light. Perhaps you have a defective oil pressure switch but if the light is on of flashing I would have my car towed and checked out to potentially avoid expensive damage.