CAN, CAN-FD and DoIP: How Modern Vehicle Networks Changed Diagnostics

The connector under the dash has not changed much, but what flows through it has. Understanding CAN, CAN-FD and DoIP explains why some tools cover the newest cars and others stop at a certain model year.

Classic CAN

Controller Area Network (CAN) has been the diagnostic backbone since the late 2000s. It is robust and well understood, but its data rate (up to 1 Mbit/s) and small frame size (8 bytes) limit how much information can move at once — a constraint as cars added dozens of modules.

CAN-FD

CAN-FD ("Flexible Data-rate") keeps the same wiring but allows larger frames (up to 64 bytes) and faster data phases. Many vehicles from roughly 2020 onward use CAN-FD for diagnostics. A tool built only for classic CAN may fail to communicate with these modules even though the plug fits.

If a newer vehicle "won't connect" with an older tool, the cause is often CAN-FD, not a faulty cable.

DoIP

Diagnostics over Internet Protocol (DoIP) runs diagnostics over automotive Ethernet, enabling far higher bandwidth for tasks like ECU flashing and complex coding. Premium and EV platforms increasingly rely on it. DoIP support is now a key differentiator between entry-level and professional tools.

The gateway question

Many recent vehicles (notably FCA/Stellantis) place a security gateway between the OBD port and the vehicle network. Full read/clear and bidirectional access may require authenticated entry. iCarsoft provides dedicated FCA/CAF gateway solutions for exactly this.

What it means when buying a tool

Check that any tool you consider lists CAN-FD and DoIP if you service late-model vehicles. See protocol support across the iCarsoft range.