Since libertys were made after 96 you just need to hook it up to an OBDii code reader to retrieve and reset the codes. Since it aids them in selling parts most parts stores will read your codes for free. This is just an indication of what sensor or system is not reading or operating correctly, diagnosing the exact problem will still be necessary. Some codes are easily interpreted and some leave more questions than answers.
I'd like to add something to this persons answer. If your liberty has a digital odometer you can pull the codes yourself. This is how you do it. Turn the ignition to the on position and push and hold the trip meter setting until it registers zero. Turn the ignition switch to the off position,then turn it to the on position,turn again to the off position and to the on position and this has to be done within five seconds. You should see your codes scrolling on your odometer. When it is finished it will say "done". If you didn't write all of your codes down, repeat the steps. Here's another way. Put key in ignition,push down the odometer reset button then turn key to the on position and release the reset button and the computer will start it's countdown showing you the serial number and then the codes. Hope this info was helpful to all who own Chrysler and Jeep autos with digital odometers.
Misfire code
Cylinder #4 misfire.
what is this code p1491 on 2003 jeep liberty
Trouble code P0605 means: Internal TCM Error
Trouble code P0734 means:Gear 4 incorrect ratio
Diagnostic code 43 in the 1997 Jeep Grand Cherokee refers to an issue with the distributor. This often causes the Jeep to stall at operating temperature.
trouble code p-0837 fo jeep liberty
http://www.jedi.com/obiwan/jeep/dtc.html
O2 sensor or wiring
catalytic converter circuit
Trouble code P0442 means:Evaporative emission control system leak detected (Small leak)
Trouble code P0700 means: Automatic Transmission Control System Malfunction You need to check the TCM for codes.