Check all the fuses under the hood and inside the cabin.
Make sure the battery terminals are very clean and tight...as stated check the negative battery lead to chassis is clean and tight.
If nothing there....your ignition switch/actuator pin assembly may have failed.
The Actuator Pin assembly turns the ignition switch when you rotate the ignition key...often the Actuator Pin Assembly slightly fails so you get ignition lights ON but no start but it is possible that it has completely snapped so the ignition switch is sitting in its home position.
Remove the plastic covers over the steering column...male Torx bit.
Remove the ignition switch off from the actuator pin assembly...smaller Torx male bit. This needs a Security Male Torx bit that has a hole down its center.
Check if any debris falls down as you remove the ignition.switch...this means the actuator pin assembly has failed.
You can insert the ignition key into the ignition slot and turn it fully ON. This enable SKIS and disables the steering wheel lock.
With Jeep in Park or Neutral rotate the ignition key with a small flat screwdriver...hopefully ignition lights come ON and you can start and drive the Jeep.
If the Actuator Pin Assembly has broken you can get one from Dorman...Dealers do not keep it.
If the above does not help....check for voltage around the ignition switch with a meter.
You can download the 2005 Jeep KJ Service Manuals here...section 8W has the wiring diagrams.
www.colorado4wheel.com/manuals/Jeep/KJ/
