2003 Subaru Outback OE Wiring Harnesses & Stereo Adapters Subaru Outback 2003, 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 least a lot simpler. 2003 Subaru Outback Trailer Wire Harness and Connector Equip cars, trucks & SUVs with 2003 Subaru Outback Trailer Wire Harness and Connector from AutoZone. Get Yours Today! We have the best products at the right price.