If your buddy's light won't go out his axle may be stuck in 4wd. The switch for the light is located in vacuum actuator on the front axle, passenger side and should only go on when the collar is the front wheel locked position. It may be a bad switch or the vacuum hose to the actuator is off or leaking. Better check it out before he wears out his tires.
Just noticed you are asking about a 1500, I don't know anything about them though it may be the same.