Sumitomo Electric Produces Wiring Systems That Enable Communication Across Modern Vehicles

The Quiet Backbone of the Digital Car

Modern vehicles are often described through their visible technologies: batteries, displays, driver-assistance systems, connectivity, and software. But none of those functions work without the physical layer that links them together. Sumitomo Electric describes wiring harnesses as indispensable components that transmit power and signals throughout the vehicle, and the company’s automotive business has built a global presence around that role. In its latest integrated reporting, the group says harnesses made by the company are used in one in four vehicles worldwide.

That scale matters because the wiring system is no longer just a passive bundle of cables. In a vehicle filled with cameras, sensors, displays, battery systems, and electronic control units, the harness becomes the physical architecture of communication. McKinsey notes that some premium vehicles now contain 150 or more electronic control units, and that next-generation zonal architectures are being adopted precisely to simplify this growing complexity.

Why the Automotive Business Matters to Sumitomo Electric

For Sumitomo Electric, this is not a peripheral activity. In FY2024, the group reported total net sales of ¥4.6798 trillion, with the automotive segment contributing ¥2.7347 trillion and operating profit of ¥172.4 billion. That means automotive accounted for well over half of group sales and remained the company’s single largest business segment. The group also reported roughly 288,000 employees in FY2024 and approximately 290,000 employees across more than 400 group companies as of March 2025.

That financial profile helps explain why Sumitomo Electric continues to position wiring systems as a strategic platform rather than a mature commodity. Its 2025 integrated report frames the automotive segment around “connection business” growth, with an explicit focus on electrification and high-speed communication. In other words, the company is betting that the future value of the harness lies less in traditional copper routing alone and more in how it evolves to support the next vehicle architecture.

From Distributing Power to Carrying Data

The most important shift in the automotive wiring business is conceptual. Historically, harnesses primarily distributed electrical power and low-speed signals across the vehicle. Today, they must also support high-bandwidth communication between ADAS modules, displays, cameras, ECUs, and central computers. Sumitomo Electric’s own product portfolio reflects that transition: its automotive high-speed communication cable assemblies are designed for applications such as automotive Ethernet, USB, LVDS, GVIF, and GMSL, serving systems including ADAS, infotainment, cameras, displays, and ECUs.

Its technical reviews show the same direction of travel. The company has published work on 100 M in-vehicle Ethernet, secure automotive Ethernet protocols, and high-speed transmission sub-harnesses for automated driving, noting that rising sensor loads, especially from technologies such as LiDAR, require faster in-vehicle data communication and new wiring and connector designs that can meet stricter communication standards.

Electrification Changes the Economics of the Harness

Electrification does not reduce the strategic importance of the wiring system. It changes where the complexity sits. Sumitomo Electric’s automotive roadmap now includes high-voltage wiring harnesses, battery wiring modules, high-voltage junction blocks, battery cooling hoses, and EV charging and discharging management systems. Its technical publications also highlight mass-produced battery connection parts such as battery wiring modules, high-voltage junction boxes, and battery-pack wiring harnesses.

That matters because electric vehicles place new demands on interconnects: higher current, tighter packaging, stricter thermal requirements, and greater reliability around battery systems and power electronics. Sumitomo Electric has spent years developing aluminum harnesses and high-voltage interconnection technologies as part of that response, while also expanding adjacent battery-related products such as tab leads and wires for automotive use. The result is that the harness business becomes more central, not less, as the car shifts from mechanical complexity to electrical complexity.

Optical and Ethernet Technologies Point to the Next Phase

The next frontier is not only electrification but bandwidth. In December 2024, Sumitomo Electric said it had led the ISO document development initiative behind ISO 24581, an international standard for in-vehicle optical harnesses. The company argued that conventional copper or aluminum harnesses are not expected to meet all future transmission-speed requirements for advanced automated-driving systems, and that optical harnesses could support communications of up to 100 Gb/s while offering low loss, high noise resistance, longer communication distance, and more flexible ECU placement.

This is strategically significant because it shows how Sumitomo Electric can combine two parts of its broader industrial base: automotive harness expertise and optical communications technology. The company explicitly describes the optical-harness milestone as the product of collaboration between those two business areas. That kind of cross-segment capability is hard for a narrowly specialized supplier to replicate and may become more valuable as vehicles increasingly resemble rolling networks rather than isolated machines.

Zonal Architecture Will Reshape the Product, Not Eliminate It

A common assumption in the industry is that zonal architecture will reduce the role of harness suppliers. The better reading is that it will change the specification of the product. McKinsey argues that fifth-generation zonal architectures can reduce wiring-harness complexity, support standardization, and enable greater production automation; it also notes that wiring harness costs in modern vehicles can account for around 20 percent of total E/E architecture budgets.

OEMs are already moving in that direction. BMW says its Neue Klasse introduces a radically simplified zonal wiring harness that uses 600 meters less cable and is 30 percent lighter than the previous generation. For a supplier such as Sumitomo Electric, that does not imply irrelevance. It implies a new design brief: fewer, lighter, more standardized, higher-bandwidth, and more automation-friendly harness architectures, integrated with zone controllers and central compute systems. That aligns closely with Sumitomo Electric’s current product examples, which include split wiring harnesses, high-speed communication wiring harnesses, and zone ECUs.

Manufacturing Is Still the Hard Part

The strategic challenge is not only technological. It is industrial. Wiring harnesses remain labor-intensive and difficult to automate at scale. Sumitomo Wiring Systems, the core wiring-harness company within the group, has described harness production as mostly handmade and historically dependent on large global labor networks. That manufacturing reality is one reason the business has traditionally been difficult to localize and standardize.

Sumitomo Electric’s response has been to redesign the manufacturing model alongside the product. Its integrated report highlights split harnesses, supply-chain visualization, and manufacturing innovation, while company materials describe efforts such as e-STEALTH W/H and automated set operations aimed at supporting local production, lower part counts, and better resilience. In a world shaped by tariffs, regional production shifts, and supply-chain risk, that manufacturing evolution may be as important as any single new connector or cable technology.

The Opportunity Is Real, but So Are the Risks

The company’s own reporting is clear that the opportunity is not one-directional. Sumitomo Electric warns that additional U.S. tariffs, slowing demand in China and Europe, and softer wiring-harness orders could weigh on the business even as hybrid demand remains solid and CASE-related product development progresses. That is an important reminder that this remains a scale-heavy, customer-concentrated, and operationally demanding industry.

Still, the broader positioning looks strong. Sumitomo Electric combines materials science, connector technology, cable manufacturing, high-voltage systems, and optical communications under one industrial umbrella. Its product pages emphasize one-stop service from wire development to cable assembly, and its automotive strategy increasingly centers on exactly the areas where modern vehicles are becoming more demanding: electrification, high-speed data transmission, and connection-system redesign.

The Strategic Meaning of Sumitomo Electric’s Wiring Business

The central lesson is simple. As cars become more software-defined, the physical system that carries power and data becomes more strategic, not less. Sumitomo Electric is not merely supplying bundles of wire to an old automotive model. It is repositioning its wiring business around the communications and power architecture of the next vehicle generation.

That makes the company important in a way that is easy to miss. The future of the car will be shaped by software, compute, sensors, and batteries. But those technologies only become a functioning vehicle when a supplier can connect them reliably, at scale, under harsh conditions, and at acceptable cost. Sumitomo Electric’s wiring systems business sits precisely at that intersection, which is why it remains one of the more consequential enablers of communication across the modern vehicle.