i just did this in my 05 silverado 1500 for my D3....you have to strip the D3 ILL wire and connect wire to it (some 18 gauge) and run that wire to light switch harness behind the dash...for my truck the dimmer wire to tap it into was the brown/white wire...take the light switch harness off and then pull the harness plug out and the brown/white wire was on the bottom left when looking at it from where the wires go in the harness...