CAN Bus Vehicle Interface
Definition of the Controller Area Network (CAN bus): how automotive ECUs communicate and how shared fleet telematics interface with door locks and ignitions.
The Controller Area Network (CAN bus) is a vehicle communications bus that lets electronic control units (ECUs), such as the engine control module, central locking and instrument cluster, exchange data without a host computer.
How the CAN Bus Works
Bosch developed the CAN bus in the 1980s. It carries data over a twisted pair of wires with the signals CAN high and CAN low, using differential signalling:
- Message-based broadcasting: ECUs send messages with an identifier across the network. Each receiver decides from the identifier whether to process the message.
- Noise immunity: Differential signalling makes the bus resistant to the electrical noise common in vehicles.
The Role of CAN Bus in Connected Mobility
Retrofitted telematics units can use the CAN bus to trigger vehicle functions and read data:
- Remote lock and unlock: The unit sends commands to the body control module so the doors can be opened from a smartphone.
- Start permission: Depending on the system, the car stays immobilised until the person who booked it starts the rental in the app.
- Telemetry: Fuel or charge level, odometer and other values come straight from the car's own sensors.
CAN Bus vs. Diagnostic OBD-II
The OBD-II port is designed for reading diagnostic data. Access to the CAN bus behind it can also reach actuators such as door locks. Neither is the only route: many newer cars can be unlocked and read through the manufacturer's own connected-car interface, with no hardware fitted.
Related Terms
Sources
Retrieved on 14 September 2026.
- Wikipedia: CAN bus, "Development of the CAN bus started in 1983 at Robert Bosch GmbH. The protocol was officially released in 1986" and "The wires are a twisted pair [...] Two signals, CAN high (CANH) and CAN low (CANL)"
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