kevinferron.comKevin Ferron

Electrical and electronic architecture

From a controller per function to domains, then zones, then a few central computers: what moves and what the wiring harness gets to lose.

  • Domain
  • Zonal
  • Central compute

Open the hood of an older car and you find a controller for almost everything: one for the door, one for the mirror, one for the wipers. Each one has its own software and its own wires back to whatever it talks to. It works, and it is how most cars got built.

The trouble is the pile: more boxes, more connectors, more wire. Sources disagree on how many controllers a car has and how heavy its harness gets, so the page shows both sets of numbers side by side rather than pick one.

The first fix was to group controllers by job. A domain controller takes over powertrain, or chassis, or body, or infotainment. That cuts the box count but not the wiring: a wire still runs from the mirror to the body domain, wherever the body domain sits.

The zonal idea groups by place. A zone controller handles whatever is nearby (the drawing puts one in each corner of the car, which is the drawing’s choice), and the zones are joined by an Ethernet backbone. The wires get short, and the logic can move to central computers.

The drawing is a sketch of that idea on one outline, with a made-up count of controllers at each step. The figures beside it come from a supplier slide, a white paper and a peer-reviewed model, and each says what kind of number it is.

A controller for each function

Every function brings its own controller and its own wires. The drawing gives each load an ECU of its own.

  • sensor or actuator
  • ECU

Drawn here: 16 ECUs and 32 wire runs, illustrative. The drawing shows the idea, not the count in any real car.

What the sources say at this stage

  • ECUs in a car

    30 to 100+

    Visteon (2019), slide labelled "Yesterday", the domain-ECU stage

    as reported

  • ECUs in a luxury vehicle

    more than 100

    Park et al. (2024), citing Leigh and Duwe (2021) and a Ward's Auto piece

    as reported

Where the sources disagree

Both ranges are shown. They come from different years, different vehicles and different ways of counting, and nothing here averages them.

How many ECUs

  • 30 to 100+ Visteon (2019), slide labelled "Yesterday", the domain-ECU stage
  • more than 100 Park et al. (2024), citing Leigh and Duwe (2021) and a Ward's Auto piece

How heavy and long the harness is

  • up to 80 kg and up to 5 km Visteon (2019); it calls the harness the third heaviest part and the third costliest component
  • up to 60 kg and up to 1.6 km Park et al. (2024), citing Stillig and Parspour (2021)

Not in any source used here

  • An ECU count for a named production vehicle.
  • How many zone controllers production cars use.
  • Harness weight saved on a named production vehicle.

The three generations (legacy domain, transitional domain controllers, then zonal plus central compute) follow SDVGuru, an opinion piece. None of its numbers is used here.

Sources

  1. Visteon, 2019 Zonal EE Architecture: Towards a Fully Automotive Ethernet-Based Vehicle Infrastructure (IEEE SA presentation). 24 September 2019.

    • Harness weight and length figures
    • Zonal architecture: short connections to zone ECUs, excluding the backbone
    • Slide figures
    • ECU consolidation roadmap slide: "30 - 100+" ECUs
    • ECU consolidation roadmap stages
    • Harness weight, length and labour (1000+ production minutes)
    • Case study: 50% and more saving in harness length
    • Case study: the trade-off resolves at 6 to 11 zones
    • Maximum wiring connection length < 3 m, excluding the backbone
    • Zonal gateway interfaces

  2. Aptiv, 2021 Zone Controllers Build Bridge to Tomorrow’s Technology (white paper). 2021.

    • Controller counts
    • White paper figures
    • Study for one OEM: 9 ECUs consolidated, hundreds of wires eliminated
    • Study for one OEM: 8.5 kg weight reduction
    • Doorsill example: cabling assembly space cut by a factor of 4
    • Smart fusing lets wires shrink by about one gauge
    • Labour is roughly half of harness cost; estimated rise of 25% to 50%

  3. Park et al., 2024 Analysis of E2E Delay and Wiring Harness in In-Vehicle Network with Zonal Architecture, Sensors 24(10):3248. 2024, doi:10.3390/s24103248.

    • Modelled harness figures
    • Peer-reviewed model
    • Background: luxury vehicles typically have more than 100 ECUs
    • Background: harnesses up to 1.6 km and 60 kg
    • Model result: harness-length reduction with 3 zones
    • Model result: harness-length reduction with 6 zones
    • Model result: harness-length reduction with 8 zones

  4. SDVGuru SDV Architecture 2026: The Definitive Guide (S. Amin). June 2026; framing only, no figures.

    • Framing only: domain, then zonal plus central compute

Everything here is paraphrased from the pinned sources, not quoted, and figures are attributed to them. Anything illustrative is labelled as such. Where a source is silent the page says so instead of filling the gap.