Porsche Cayennes have an electrical "kill switch" that deploys during an accident, to help avoid igniting fuel that may leak after the crash. It is located under the driver's seat in the main power distribution panel. Some Cayennes use a Ford VCM II that can be reset, while others use an explosive devise that requires replacement. Please take your Cayenne to a qualified Porsche repair facility and inform them of your accident. This type of repair should not be performed by anyone except professionals, due to the possible dangers involved if you were to be in a crash at a later date and this system might fail to operate correctly. No one wants to die from a preventable consequence!