Vehicle FlexRay Protocol introduction

FlexRay Protocol in Vehicles
FlexRay Protocol in Vehicles

The FlexRay protocol is a vehicle fast, reliable and time-triggered protocol that offers the delivery of communication data and information among the modules located in the vehicle in a Realtime.

The protocol speed varyes from 500Kbps to 10Mbps (up to 20 times faster than CAN-BUS protocol), interrupts are working based on Event Trigger or Time trigger.

FlexRay is a serial communication technology that is used in particular for data communication in very safety-critical use areas in the automobile such as Engine Control units, Brake Systems, Steering systems…etc

FlexRay layouts include the Multi-drop Bus, the Star Network, and the Hybrid Network. The Multi-drop Bus topology is the same as in CAN and LIN systems, and it uses a single bus of two twisted wires to connect multiple modules together, this system is helpful in implementing with other systems due to the similar layout of CAN and LIN networks. The Star Network topology consists of multiple ECUs connected to a central active node.

Other Modules connected to the FlexRay network can communicate with other non Flexray modules via the vehicle Gateway, the vehicle gateway will convert the in/out messages from/to Flexray.


FlexRay has been developed by the FlexRay Authorty (including BMW, Bosch, Volkswagen, Daimler).

BMW X5 E70 series (2008) was the first vehicle to have a FlexRay network fitted. It is implemented for the Vertical Dynamics Control Module, which controls the suspension height for each individual suspension unit.

Later on, FlexRay used widely in BMW next generations (the F/G series) to include many modules like the ECM (DME/DDE).


FlexRay network usually is configured in a Star Bus, this way the system will keep operating even when a module fails. Also, it is an advantageous setup when long lengths of wiring are required, as normal electrical interference will only affect one leg of the network due to this configuration. A module unit is located in each corner of the vehicle.

Connect BMW DME On Bench

Autohex and Hexprog users who need to work on bench with a BMW DME/DDE has FlexRay netwrok intigrated in, they have to connect the FlexRay twisted wires from DME/DDE to the Gateway (FEM, BDC or ZGW), they also required to connect the CAN BUS network from the DME/DDE to the Gateway.

Without this setup, the DME/DDE will not communicate by OBD.

For more information please contact our technical support team.

Last Update: 5/4/2022
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