The FCM on the 2005 KJ has a reputation for getting splashed with mud, water, snow with salt etc. which can cause the connector to get rusted and cause a bad connection. The 2006 models have the FCM moved inside the cabin on top of the Junction block...away from harm from the elements!
So I would advise you pull this module out and check the connector pins are clean and make firm contact.
As stated the FCM does not have any active components inside it so there is not really anything to "blow up" but it would seem from the advice posted here that there is a large range of Chrysler vehicles that used this FCM so a boneyard may have what you need.