Try this: Turn the ignition ON, then OFF, ON, OFF,ON. All within about 15 seconds and without cranking. It's known as the "Key Dance" and works with most of the newer Mopar and Jeep Vehicles.
Then your check engine light will flash out the codes (IE: for code 12, Flash, 1-2 Pause, Flash, Flash), or sometimes the digital odometer will display them numerically.
Keep in mind, your's is OBDII and will only display the older two digit (IE: 12) codes. The code displayed could have more than one meaning behind it, which is what you would need the scanner to distinguish.
This does not work Past the year 2K vehicles or on RENIX Jeeps. Those WILL require a scanner to read the ECM memories.