Finding
Harness assembly is still mostly manual and concentrated in low-wage countries, so architecture changes - zonal layouts and 48 V - matter more for cost than any manufacturing advance
Wiring harnesses are built largely by hand on assembly boards in Mexico, Morocco, Tunisia, Romania, Serbia, Ukraine, the Philippines and China. When Russia invaded Ukraine in 2022, Leoni and Fujikura harness plants in western Ukraine stopped and Volkswagen and BMW lines in Germany halted within days.
Yazaki, Sumitomo Electric, Aptiv, Lear, Leoni, Furukawa, Fujikura and Motherson supply most of the world's harnesses. China's Luxshare took majority control of Leoni in 2025, and Chinese harness makers such as Kunshan Huguang and Tianhai (THB) grew with BYD and the domestic EV boom. Harnesses are designed per vehicle, so supplier changes require requalification, and the work moves only when programs change.
The architectural fixes cut wire rather than labor. Zonal layouts let local controllers aggregate nearby loads and talk over Ethernet; Rivian said its Gen 2 R1 removed 1.6 miles of wiring and 44 pounds. Tesla's Cybertruck, built at Giga Texas, moved the low-voltage system to 48 V, cutting current fourfold for the same power. On the high-voltage side, 800 V platforms halve current for a given power, shrinking orange cable cross-sections; aluminum conductors and busbars replace copper where packaging allows. See Zonal Architecture and Copper Conductors.
Elements
What the harness system includes
| Element | Role | Examples |
|---|---|---|
| High-voltage cabling | Propulsion and charging energy | Shielded orange cables, battery-to-inverter leads, charge-port lines, busbars |
| Low-voltage harnesses | Power and signals to controllers, sensors, actuators | Body, cockpit, door, ADAS and zonal harnesses |
| Connectors and terminals | Separable interfaces | Sealed HV connectors, multipin LV connectors, terminals |
| Protection and switching | Isolate and protect circuits | Fuses, pyrofuses, contactors, relays, service disconnects, HVIL loops |
| HV-to-LV conversion | Feeds the LV bus from the pack | DC-DC converter |
| Distribution hardware | Aggregate and route power | Power distribution units, fuse boxes, junction boxes, eFuse zone controllers |
Architecture
From distributed to zonal
| Architecture | Pattern | Strength | Tradeoff |
|---|---|---|---|
| Distributed | Long runs from a central fuse box to dozens of ECUs | Familiar, proven | Heavy, complex, hard to automate |
| Domain | Functional domain controllers (body, chassis, cockpit) | Fewer ECUs | Wiring still routed by function, not location |
| Zonal | Zone controllers serve local loads; Ethernet backbone to central compute | Shorter runs, fewer connectors, more automatable | Value shifts to zone controllers and software; full redesign needed |
Supply chain
Where the harness supply chain tightens
| Area | What gets tight | Suppliers | Effect |
|---|---|---|---|
| Conductors | Copper and aluminum cable, HV insulation | Leoni, Sumitomo, Furukawa, Coroplast, Huber+Suhner | Cost pressure, redesign |
| Connectors | Sealed HV connectors, LV terminal families | TE, Amphenol, Aptiv, Yazaki, Rosenberger, Molex, AVIC Jonhon, Luxshare | Requalification delays late changes |
| Safety devices | Contactors, pyrofuses, service disconnects | Hongfa, TE, Panasonic, Sensata, Autoliv, Littelfuse, Mersen | Program delays |
| Assembly capacity | Labor, boards, test fixtures | Mexico, North Africa, Eastern Europe, Asia | Ramp speed and quality; exposure to local disruption |
Sources
Sources and scope
- Scope
- EV Wiring Harness
- Sources
- Rivian (Gen 2 R1, 2024); Tesla (Cybertruck, 2023); Reuters reporting on Ukraine harness plants (2022); Luxshare and Leoni disclosures
- Updated
- October 2026