2002 Hyundai Accent Cannot pump gas and engine light on

I have been having trouble for about four months pumping gas into my car. It clicks when I pump gas so I cannot tell if it is full or not. Just around the time this started happening my check engine light came on. The first thing I did was call my mechanic. I brought it in and he changed out one of the pumps and said this would not gaurantee anything because he has not seen anything like it. I went to have it scanned for a code and the code was DMTL or DTML leakage. I had my oil changed and they insisted on scanning it again and said it was a sensor. I have had my code cleared by detaching the battery and having the code cleared. I was also asking my mechanic if it the two could be associated with eachother (the check light engine being on and me not being able to pump gas) which he said no. I am thinking about taking it into the dealership but I don't want to pay an arm and a leg for it but I have to get my inspection sticker. The car runs fine it is just pumping gas and having to keep pumping and it clicking to fill the tank and I do not even know when it is full. I have tried different angles and everything. What possibly could be wrong? Are the two associated with eachother?