My "Service 4WD" light came on, and ALL lights on my selector switch are lit.

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All lights on my selector switch are lit, and my "Service 4WD" light came on after I replaced the belt tensioner assembly in my engine. I can't believe those things are linked, so something else must be wrong. The problem is I've only seen posts where NONE of the lights are lit on the selector switch, but on my truck ALL of them are lit. I did confirm it happens every time it starts now, and I am able to drive it normally with no strange sounds or movements. I didn't want to drive it a long distance, though. About a year and some change ago my transfer case froze up, stopping my truck dead in its tracks in the middle of the street. It got replaced with a junkyard part, but I didn't have any lights or warnings whatsoever when that happened. I'm afraid to drive it now just in case a similar thing happens.