2008 Chevy HHR OE Wiring Harnesses & Stereo Adapters Metra®Aftermarket Radio Wiring Harness with OEM Plug Chevy HHR 2008, Aftermarket Radio Wiring Harness by Metra®, with OEM Plug. For aftermarket stereo. Metra preassembled wiring harnesses can make your car stereo installation seamless, or at 2008 Chevrolet HHR | Stereo Wiring Diagram 2008 Chevrolet HHR Stereo Wiring Information. Radio Battery Constant 12v+ Wire: Red/White. Radio Ground Wire: Black/White. Stereo Power Antenna Trigger Wire: Pink. Stereo Amp Turn-On Trigger Wire: Pink. Left Front Speaker Positive Wire (+): Tan. Left Front Speaker Negative Wire (-): Dark Green.