Gateways and Multiple Buses
Modern cars run several networks behind a gateway. Learn to diagnose across them.
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What you will learn
- Identify the main networks
- Explain the gateway role
- Localise faults on a multi-bus vehicle
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Modern vehicles are not one network. A high-speed powertrain CAN, a slower body CAN, LIN for simple devices and sometimes FlexRay or Ethernet coexist, joined by a central gateway. Each bus has its own wires, termination and diagnostics.
This matters because a module may not be reachable through the OBD connector directly: the request is routed by the gateway. When systems vanish, first establish which bus they belong to, then measure that bus rather than assuming a single network.
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Key points
- Identify the bus before measuring it.
- The gateway explains why some modules are unreachable.
- A single bus fault only affects the modules on that bus.
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Key points
- Multiple buses with different speeds and jobs
- The gateway bridges them
- Diagnose the network a module actually lives on
All values shown are training examples. Real thresholds depend on the manufacturer, engine, temperature and system — always confirm with the vehicle service documentation.
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