What Is an Engine Harness? | It Still Runs The engine wiring harness then brings power back to the engine and those engine components that need it. These include the computer, the fuel injectors, the wiper and blower motors, and any other electrical component located under the hood. Engine Harnesses - Rywire Rywire Motorsport Electronics specializes in wire-tuck (tucked), high performance, Mil-Spec engine harnesses. Rywire Brake Tuck, Clutch lines and Custom Radiators are popular as well. We sell & troubleshoot AEM, Hondata, Chipped ECU's, AIM Sports and MOTEC equipment.