I have a 2006 ford explorer with ~42K miles. The check engine light and gas cap light are on. I took it to autozone and they ran the code, and said it was a loose or missing gas cap, and sold me a replacement. I installed it, they cleared the code, it was great. The lights both stayed off until the next time I went to put gas in it. After it had been refueled and running about 5 minutes later the light came on again. The gas cap light stayed off. I took it back to autozone, they ran the codes and cleared them and said it was excessive vapors, but had no idea what caused it (please remember that autozone is a parts counter, not mechanics) It was fine again, until I went to put gas in it again, now the CEL and gas cap light are both on again. They do not turn off after a while, I have reseated the gas cap to confirm its tight, it clicks. Fuel Mileage and performance are unchanged. I am going to take it to a different autozone to actually get the code in the next day or two, but would like some input from enthusiasts as hopefully you guys have seen this problem before.