Welcome to the forum, was it high or low beams that were on? The truck has an auto lamp module that I think has shorted out here is a wiring diagrams for the headlight so you can see how the system works and I have included the auto lamp module so you can unplug it to see if this is the problem.
The autolamp system provides light-sensitive automatic on-off control of the exterior lamps normally controlled by the regular headlamp switch. The autolamp system keeps the lamps on for a preselected period of time (20 seconds) after the ignition switch is turned off. The preselected time lapse is not adjustable.
Check out the diagrams (Below). Please let us know what happens.
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Tuesday, November 3rd, 2009 AT 11:51 AM