I have a 99 XJ I just recently got and it had a few codes. It was throwing p0123 and p0500. I replaced the TPS and did plugs, wires, cap, and rotor and now it idles perfect and the p0123 is gone (for now). When the PO did the plugs they just put the wires into random plugs so it wasn't firing correctly so I'm wondering if that had anything to do with it..... but for the speed sensor. I bought a new one and the bolt that goes in it just spins. I can see the back threads and they are moving, but now luck of it coming out. Wondering if there are any tips/tricks or if I have to take out the whole thing including gear and replace it all.

 

On the transfer case back housing? Its aluminum and probably stripped out. You can remove the back housing without too much drama and heli-coil it to repair the thread