I have a low mileage car (62,842 miles). The Check Engine Light came on today. I undersatnd General Motors diagnostics but I am new to MB. The car appears to be running normally. Is there a way to check what sensor may be the cause? How do I reset the light and/or clear codes? I found a test connector with a reset button & LED. Pressing the button with the engine running turns on the LED, is that normal? Thanks for any help.