One problem related to wiring has been reported for the 2007 Mercedes Benz GL450. The most recently reported issues are listed below.
Head lights went off in the while traveling due to defecting wiring system. According to experts mb used an inferior and unsuitable material for the insulation on the electrical wires of some of the Gl450 models. This insulation prematurely disintegrates under normal use causing the wires it is designed to protect and insulate, to short causing many problems.