Controller Area Network (CAN)
A shared two-wire differential communication network linking vehicle controllers, batteries and instruments, and a key source of onboard operating data.
Definition
Controller Area Network connects electronic control units over a shared differential pair rather than separate point-to-point wiring. Drive controllers, BMS, instruments and steering units exchange operating values and fault states. A correctly engineered data terminal can acquire these native signals without adding separate sensors for every parameter.
Why Use a Shared Bus?
Shared wiring reduces harness weight, cost and complexity as nodes are added. Nodes receive messages and filter identifiers of interest. Differential signalling rejects interference affecting both wires similarly, helping communication in electrically noisy motor and contactor environments.
Messages and Arbitration
Classical CAN frames carry an identifier and up to eight data bytes. The identifier describes message content rather than a recipient address. Lower numeric identifiers win bitwise arbitration; other transmitters wait and retry. Heavy bus load can delay lower-priority traffic, so apparent missing data may be a timing issue.
Protocols and Signal Definitions
CAN specifies transport, not the meaning of every byte. Upper-layer protocols or manufacturers define identifiers, scaling and fault formats. Industrial-vehicle definitions differ across brands, models and years. Confirm the correct version and adapt decoding rather than assuming identical identifiers mean identical signals.
Reading versus Writing
Passive listening avoids issuing control commands and is the usual acquisition approach. Transmitting can affect vehicle behaviour and requires OEM-defined interfaces and validation. Even a read-only installation must preserve termination, wiring and signal integrity; incorrect physical connections can still disrupt communication.
Fault Investigation
Widespread loss suggests physical wiring, termination, power or a disruptive node. Missing individual signals may indicate a disconnected source or wrong definitions. Intermittent faults often involve connectors, damage, shielding or interference. Qualified personnel should check the physical layer, then message presence and timing, then decoding, following the relevant service documentation.
Frequently Asked Questions
Can connecting a terminal affect the vehicle?
Passive monitoring sends no control requests, but electrical installation must still preserve the bus. Writing messages directly affects controls and needs OEM approval and testing.
Why is decoding not universal across brands?
CAN defines how frames travel, while manufacturers or higher-level protocols define their contents. Different model and firmware versions can require different signal maps.
Related Terms
From Concept to Fleet Deployment
AI-Driven provides ADAS perception, smart onboard terminals and fleet management platforms for industrial vehicles, turning these concepts into real gains in fleet safety, efficiency and maintenance.
This glossary covers general industry concepts for technical reference and knowledge sharing. It contains no proprietary information from any specific manufacturer. For equipment specifications and operating procedures, always refer to the OEM documentation.