What Are Each Wire Color for the Headlight Wire Harness In the diagram, the top wires are voltage, bottom wires are ground. The dimmer switch is part of the ground circuit, if you wan t to word it that way. The low beams ground through the headlamp relay in diagram. The high beams ground through dimmer switch ground. The ground wire location is the same for high and low. Sorry it took so long. 2003-2005 Chevrolet Impala Vehicle Wiring Chart and Diagram Listed below is the vehicle specific wiring diagram for your car alarm, remote starter or keyless entry installation into your 2003-2005 Chevrolet Impala information outlines the wires location, color and polarity to help you identify the proper connection spots in the vehicle. Low Beam Headlamp Problem - 2005 3 Impala | Impala Forums Low Beam Headlamp Problem - 2005 3 Impala. Jump to Latest Follow but the lows will not. The wiring diagram I'm using shows a hard path from "Hot at all times" to ground when the Multifunction switch is in Low and the Headlamp then there is a break in the wiring leading to the headlight, and the wiring will need to be replaced. Good SOLVED: 03 Impala Headlight relay- How to tell if it is ba Need wiring diagram for headligt on 2003 chevy impala with 3.8 cu engine Sounds like a short or the relay is going bad to the headlamps. You may be able to google for the diagram but probably will need to get a repair manual from the nearby auto parts store for appx $25.