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UDS Message Structure

UDS Message are of following Types-

Request Message– Used to send by Tester/Client to the ECU for preforming any action .

Positive Response Message– This frame is sent by ECU to Tester if received request message is correct.

Negative Response Message– This frame is sent by ECU to Tester if request message is not correct e.g. Incorrect Service ID or Data length or Sub function in request frame.

Service Identifier –  Service Identifier is 1 byte long unique ID defined in 14229-1 to perform specific operation in ECU.

Sub-function – It is an optional field and sub-part of service ID.


Service ID : 0x10 (Session Control)

Sub-Function – default session, programming session ,extended session

So you can see Tester can Send following request to ECU for Session change.

Structure of UDS Frame over CAN

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