Checked the manual but could find nothing-What is the little round circle-recessed cap (that you can press down on with your finger as if releasing it?) on the lower left side of back bumper. Also-how do I identify the" trailer prep package" on my SE? I called the salesman that sold me the santa fe and he could not answer. I could call the service dept. but I seem to get quicker and better answers here! Thanks, Tedrik