CAN-FD Explained

You may have heard the term CAN-FD appearing on your scan tools as part of vehicle selection options but what is it, and what benefit does it provide to us as technicians?

What is CAN-FD?

CAN-FD (Controller Area Network Flexible Data-Rate) is an enhanced version of the original CAN communication protocol, designed to meet the ever increasing data transmission requirements of modern vehicle systems. In vehicle diagnostics, CAN-FD is of huge benefit to technicians as it allows for faster and more efficient communication between the vehicle's Electronic Control Units (ECU's) and diagnostic tools, meaning the live data you're looking at is refreshed and updated on screen faster, allowing you as the technician to interpret the data more accurately and catch smaller changes.

Can-FD started appearing in production vehicles from around 2019 onwards, though it wasn't immediately widespread. As vehicle systems have become more data intensive, especially Hybrid and Electric vehicles (xEVs). Autonomous Systems, and Advanced Driver Assistance Systems (ADAS), manufacturers had to turn to a new CAN standard that could handle the higher volumes of data needed more efficiently.

Now in 2024, many modern vehicles, particularly those from leading brands such as Volkswagen, Audi, BMW, and Lexus, have integrated CAN-FD into their network architectures.

How CAN-FD Works

Data Rate
Flexible Data Length
While traditional CAN networks operate at a maximum of 500 kb - 1 Mbps, CAN-FD can transmit data at speeds of up to 8 Mbps, allowing larger amounts of data to be sent up to 8x faster for the same time period.
CAN-FD supports message sizes up to 64 bytes, compared to the standard CAN's 8 bytes. This larger payload enables more diagnostic data to be transmitted inside the single message. This is particularly usefuel for ECU's when handling large data sets, such as those from advanced sensors used in ADAS, like forward facing cameras or millimeter wave radars, or ECU's in Hybrid and Electric Vehicles (xEVs).

Application In Vehicle Diagnostics

Data Access

Fault Identification
Real-Time Monitoring
Modern vehicles, especially xEVs, generate a massive amount of diagnostic data. CAN-FD allows technicians quicker access to this data, improving the speed and efficiency of diagnosing vehicle faults and issues.
With more data available in a shorter period, diagnostic scan tools can retrieve and analyse fault codes faster, resulting in quicker identification of issues. This can be particularly useful when using scan tools or performing live data logging. With some high end vehicles having upwards of 100+ ECU's to communicate and interrogate for faults, this faster communication speed is essential for technicians to maintain efficiency.
Technicians can also view real-time live data from multiple vehicle systems simultaneously much more effectively with CAN_FD. This can be of huge benefit in helping to catch intermittent faults that only occur under specific driving conditions.

Summary

CAN-FD represent a significant forward jump in automotive diagnostics, offering faster data rates, larger message payloads, and seamless backwards compatibility with traditional CAN systems. It plays a crucial role in modern vehicles, especially Hybrid & Electric systems, enabling technicians to perform diagnostics much more efficiently. By using the existing voltage levels and 120 Ohm terminating resistors, CAN-FD maintains the same physical architecture, making it easy to integrate into existing systems. As vehicles continue to evolve, mastering and understanding technologies like CAN-FD are essential for technicians staying at the forefront of diagnostics.
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