Essentially, a modern car is a computer. They're connected to various servers providing data: from the location of a store to your favourite series.
A Brief History of On-Board Diagnostics
OBD systems, on-board diagnostics, are an important part of modern vehicles. This is the ability of a vehicle to self-diagnose and report data about the vehicle's performance and operation. Originally developed to help control emissions in California, the lack of standardization initially limited their effectiveness.
OBD-II, the successor to OBD, is advanced enough to detect potential damage to an ECU and issue a warning before failure — the classic "check engine" light. OBD-II enables bidirectional data exchange between the vehicle and external devices.
OBD-II is the most widely used interface in modern vehicles, with equivalent systems in the EU (EOBD), Japan (JOBD), and Australia (ADR). Since 1996, its use has been mandatory for all cars sold in the US. By law, it must transmit emissions-related data — but most manufacturers also include real-time ECU data streams.
K-Line
K-line is a low-speed, single-wire communication system primarily used for diagnostic purposes. It can transfer any data, limited only by its broadband capacity of 10 Kb/s.
The main limitation: only one ECU can send a message at a time. Any device on the K-Line network sees all queued messages — a security risk when transferring sensitive data.
Today, K-Line is mainly used in vehicles without a CAN bus, or where a single wire is sufficient for the task.
CAN Bus
CAN bus, or Controller Area Network, is much faster than K-line (up to 1 Mb/s versus 10 Kb/s) and can transfer more data in a single message. OBD-II now mostly runs on CAN, making it standard across cars, trucks, tractors, and industrial robots.
Unlike K-Line's sequential queue, CAN unites all ECUs into a decentralised system capable of transmitting multiple messages simultaneously. This improves throughput but introduces a different security consideration: some vehicles remain vulnerable to hacking via crafted CAN messages.
What This Enables
A wide range of apps are built using K-Line and CAN protocols — from ride height controllers to sophisticated factory automation systems that control car-assembly robots.
New vehicle bus extensions like CAN-FD are expanding the bandwidth and capabilities of in-vehicle networking, opening new possibilities for driver experiences, factory automation, and business tooling built on top of vehicle data.