The box marked DVD is the nav computer and the antenna connection is the small plug on the back of it. Make sure your antenna is plugged into the MKIV. New GPS antennas are cheap on ebay. As kiwi said, the GPS receiver is a little card with the antenna plug on one end of it which sticks out of the back of the MKIV. It is mounted inside of the MKIV. I will post a picture of one from ebay so you will know what it looks like. Do double check your antenna! Look for BMW GPS antenna on ebay to see what one looks like.