It may be different on different models and years, but on my 2009, i enter the diagnostic mode by turning the key off, then hold both the RESET and SETUP buttons and then turn the key to RUN. Instrument cluster starts in Diagnostic Mode.
From there you push the SETUP button to cycle through all of the various readings. What your looking for is the CDC screen. Record the codes it recorded and take it to your dealer. (There's a LOT of screens, so don't give up too soon).
I believe on those who have the push button start, you push the START button without placing your foot on your brake to enter the run mode.
Edited by enigma-2, 07 August 2017 - 06:06 PM.