Wiring Harness | Sumitomo - SEWS-E Wire Harness Manufacturing Wiring Harness. Did you know that automobiles today have a thousand or more connection points for circuits and wires? The central challenge of wiring harness technology lies in designing cost-effective techniques for rapidly and accurately assembling these connections. Wiring harnesses and electrical components | Products The Sumitomo Electric Group operates its wiring harness business globally to offer various products that meet the needs of the times with superb technologies and quality. The product lineup includes wiring harnesses for transmitting electric power and information in vehicles and products for environmentally friendly HEVs and EVs.