Taillight Light Explanation
Not sure if you have received an answer yet. I am new to this forum. I own a 2018 GLE400. That small section of red light on the lower left hand taillight assembly is M-B's version of a fog lamp. It is a very bright small lamp which is activated by a small push-button switch immediately to the left of the headlamp switch. It is meant to give some added warning to drivers approaching from the rear in poor visibility. When activated, a small headlamp icon appears in the right hand side of the gauge panel.