Thanks @Longdog. Will investigate further.

No, I don't mean the earth wire. I've read a lot about that one. My problem is the wire which connect to a part I don't know what it is or it does.

Thanks, its a relief. But I would like to know the part and what it does. But will leave it as is till I have found some more info about it.

I am new to Land Rover and this is my first post. My wife has a 2004 Freelander Td4. Reading through the forum I then decided to change the filter fuel myself following instructions from the forum. After changing the Fuel Filter I noticed a loose wire (Not the earth one), it's like a plug to...