Several months ago the engine light came on. My mechanic tested it but couldn't find anything. He turned the light off but it came back on a few weeks later. I brought the car back in but again he couldn't find anything. Turned the light off and again, it came back on several weeks later. This time he did a smoke test. It did not show any leaks. But he said he heard a faint hissing sound and smelled a very faint scent of gasoline in the trunk. There's just a small opening where he can see the gas tank so he suggests that I pay about $300 for the labor to get to the gas tank to see what the issue is. He said it could be a crack in the tank or one of the lines. Any suggestions about whether or not I should get that done? Or ideas about what the problem is?