Diagnosing problems with your Jeep Wrangler JK can be both frustrating and mystifying. Today's vehicles have on-board computers that keep track of what has gone wrong recently, and the computer displays this information in diagnostic trouble codes. Diagnostic trouble codes tell us what part of the vehicle has malfunctioned, and what exactly went wrong. Wrangler JK owners can retrieve codes quickly in their own driveway or garage.
Insert the key into your Jeep's ignition. Rotate it to the "On" position (third position) without starting the engine.
Push inward on the key (toward the ignition), and quickly rotate the key from the "On" position to the "Acc" position (second position) three times, ending in the "On" position.
Pay attention to the lights in your instrument cluster. If you've done everything correctly, all of the lights will light up and six dashes (- - - - - -) will appear on your odometer for a brief period.
Observe the odometer and write down any diagnostic trouble codes that it displays. The codes should appear immediately after the six dashes. If there are no codes in the Jeep's computer, the odometer will read "-done-" after the dashes.
Rotate the key to the "Off" position, and remove the key from the ignition. Look up the diagnostic codes on Project-JK to find out what they mean.
