On 2001 and newer Jeeps/Chryslers, get in the car, close the door firmly, and set the odometer to read total miles.
Then turn your key to the on position (not START, but just so the idiot lights come on), then off, then on, off, and on (leave it in this position). You should see an alpha-numeric code displayed in the odo display if something is wrong.
Jot the code down, and either ask your dealer's service dept what it means, or see if Allpar.com lists it. I have had good luck asking the dealer in similar circumstances.
This will NOT work on 2000 and older Jeeps and Chryslers, except for if you go back to the mid '90's Chryslers and before- then it does work going back at least to the mid 80's.
So....ON, OFF, ON, OFF, ON
If your doors are open, this will not work, because your odo display will instead tell you that your door is ajar.
Mopar magazine (a service oriented magazine put out by Chrysler) for the 2001 and up info, and personal experience on the '80's Chryslers.