You need to recheck your ground circuits. Go to the resources on the forum and go to the service manual section.
2006 service manual, section 8w is wiring, go to the schematics section, and go to ground schematics 8w-91
You want to look at pages 8w-91-16, ground cable g105, 8w-91-17 ground cable g107 and g108, 8w-91-20 ground cable g106
set up a multi meter to ohms. black lead to a good clean ground. now take the red lead and touch it to the eyelet of each individual ground g105, g106, g107, g108. do not touch the bolt/nut or stud.
you should be reading less than 5 ohms in each. If you are reading more than say 10 ohms, you have a problem with that particular ground connection. Clean it up and retest.
Make sure you test with the key off, doors closed, nothing on. or better yet, disconnect the battery
Note*** this is just testing the ground connection and not the circuit itself.
Inspect each of the ground circuits for corrosion starting at the eyelets and go back about 12 inches. you may have to remove wire loom. Look for a brake or swelling in the insulation.
Set you multi meter to voltage, what are you reading across the battery itself? 12+ volts
Now have someone attempt to crank the jeep over, what does the voltage drop down to?
Next disconnect the battery, remove the under hood fuse box and inspect the connectors for any signs of corrosion.
If you are not comfortable with circuit testing or doing voltage drop tests, find a local shop that specializes in electrical diagnostics.