My check engine light came on this morning and I used the key method to get code p0457, loose gas cap. Turned out to be a loose gas cap!!!!!
So just incase anyone with a Jeep doesn't know it, if your check engine light comes on you can read your codes by:
Turn key to ON without starting engine.
Press key in and hold, go quickly 3x from ON to ACC back to ON etc..., finish at ON
Your codes will display on the odometer followed by DONE.