2003 Pontiac Grand Am OE Wiring Harnesses & Stereo Pontiac Grand Am 2003, Factory Replacement Wiring Harness by Metra®, with OEM Radio Plug. For factory stereo. This high-quality Metra wiring harness is just what you need to replace your defective or aged factory wiring harness. 2003 Pontiac Grand Am Stereo Wiring Harness - autozone Equip cars, trucks & SUVs with 2003 Pontiac Grand Am Stereo Wiring Harness from AutoZone. Get Yours Today! We have the best products at the right price.