I BELIEVE MOISTURE COLLECTED IN THE BOTTOM OF THE "SPARE TIRE WELL" IN THE TRUNK- DUE TO CHANGING FLAT TIRE AND OPENING TRUNK IN THE RAIN. THERE IS AND ELECTRONIC MODULE AT THE BOTTOM OF THE "SPARE TIRE WELL BMW STOCK #W61 35 6 982 347) IT WENT ON FIRE-BECAUSE OF MOISTURE. REPAIR WAS MADE, MODULE WAS RELOCATED TO UPPER LEFT LOCATION OF TRUNK (AS WAS DONE ON MODELS AFTER 2004 LD PART IS AVAILABLE FOR INSPECTION. *AK