HOW TO: Complete!! Guide To A Headunit And Metra Wiring Jun 07, 2007The D3 has a wire that needs to be grounded, and has a metal spade to attacth to a bolt or whatever. The metra unit also as a grounding wire that i need to connect to the D3. I was told that the metra wire will be automatically grounded by the cars harness. So i wire tapped into the D3 ground instead of cutting off the spade and connecting the Car Stereo Head Unit Wire Harness - the12volt Disclaimer: * All information on this site ( the12volt ) is provided "as is" without any warranty of any kind, either expressed or implied, including but not limited to fitness for a particular use. Any user assumes the entire risk as to the accuracy and use of this information. Please verify all wire colors and diagrams before applying any information.