2006 gmc envoy: fuel tank sensor shows fuel then doesn't, bounces back & forth. i drive in the mountains and am now very paranoid that my car will run out of gas and leave me stranded on a mountain highway....very dangerous. mechanic says error code is po463. i am so afraid to drive my car alone now... so i stop gong down & then back up the hill just in case i can put in more gasoline. my car also has a drivers' side master control window that burned.... could have started a fire. when my mechanic took it apart, he showed me the burned areas,... smells bad. *tr