There are plenty of "my Jeep won't start" threads on here, with various causes.
Switch that tells the computer an automatic is in park and the clutch pedal switch on the manuals seem to be common culprits, but for those with intermittent probs and issues where you get it towed to the dealer and it fires right up- this may be whats happening.
I'll start with:
CHECK YOUR BATTERY!
and by that I mean load test it, swap it out or hit it with a charger really hard for awhile, not just put a meter on it and think "ok its got voltage, what's next?"
Everyone knows what a weak battery acts like, and how to check it with a voltmeter, etc.
But the Jeep computer TIP start deal can make it tricky to diagnose!
My Jeep, like 4 or 5 times since I got it has refused to start - turn the key and get a "chunk" sound - not the typical click of a dead battery clicking a starter relay, but the CHUNK of the starter engaging and just barely starting to turn the motor over and immediately kicking back out. Kick it a few times and it would fire right up - no slow crank or anything just spin and go like nothing was wrong, plus the interior lights would just barely dim.
So I'm defintely NOT thinking battery.
Well it was - here's what I think was happening.
The computer checks for sufficient voltage to start the motor, battery starts getting toasted and is holding a surface charge - check it with a meter and it shows sufficient voltage but as soon as there's a load (like the starter engaging) the voltage drops immediately below the required amount and the computer kicks the starter out.
The battery isn't completely toast and holds plenty of amps, just at a lower voltage than the computer will allow the Jeep to try to start at.
Bump it a few times and maybe you'll catch it where it doesn't quite drop enough and the battery puts out the amps to start it right up, but just barely above the threshold for the computer to let it try starting.
check it with a meter and with no load, the voltage shows good.
Mine did this and then wouldnt do it again for months, then finally it did it again - I got the video and 5 min later it spun right up, then the damn thing stranded me the next day.
I bumped and bumped and bumped - called a buddy for help, the second I hung up with him on his way, it cranked right up.
Anyway, I know I'm hell on my electrical system - 14+ lights, winch, etc - I know I need to go dual battery, just gotta find the $$.
Bottom line is these things are very sensitive about battery condition, and sometimes a bad battery condition is really hard to diagnose.
I have a video of the "chunk" sound so you can hear what I'm talking about, I'll insert it as soon as vimeo is done processing it so you can hear what I'm talking about - its not the typical dead battery "click" of a starter relay.
YouTube - IMG_0111.MOV