Diagnostic Service

Diagnostic services are functions offered by Servers (ECUs) to a Client via the UDS protocol. Each service is identified by a Service Identifier (SID) value.

Service Identifier

The Service Identifier (SID) is the first byte of the payload (Application Data, A_Data) in each diagnostic message.

The SID value determines whether the message is a request message or a diagnostic response. It also defines the general purpose and format of the diagnostic message.

List of all Service Identifier (SID) values and their application:

Request Service Identifier

Request Service Identifier is a subtype of SID. It is the first byte of each request message and identifies the diagnostic service for which the message is relevant.

Note

The 2nd most significant bit (bit 6) of all Request Service Identifiers is 0.

Response Service Identifier

Response Service Identifier (RSID) is a subtype of SID. It is the first byte of each response message and identifies the diagnostic service for which the message is relevant.

Note

The 2nd most significant bit (bit 6) of all Response Service Identifiers is 1.

DiagnosticSessionControl

DiagnosticSessionControl service is used to change diagnostic sessions in the server(s). In each diagnostic session a different set of diagnostic services (and/or functionalities) is enabled in the server. Server shall always be in exactly one diagnostic session.

ECUReset

ECUReset service is used by the client to request a server reset.

ClearDiagnosticInformation

ClearDiagnosticInformation service is used by the client to clear all diagnostic information (DTC and related data) in one or multiple servers’ memory.

ReadDTCInformation

ReadDTCInformation service allows the client to read from any server or group of servers within a vehicle, current information about all Diagnostic Trouble Codes. This could be a status of reported Diagnostic Trouble Code (DTC), number of currently active DTCs or any other information returned by supported ReadDTCInformation SubFunctions.

ReadDataByIdentifier

ReadDataByIdentifier service allows the client to request data record values from the server identifier by one or more DataIdentifiers (DIDs).

ReadMemoryByAddress

ReadMemoryByAddress service allows the client to request server’s memory data stored under provided memory address.

ReadScalingDataByIdentifier

ReadScalingDataByIdentifier service allows the client to request from the server a scaling data record identified by a DataIdentifier (DID). The scaling data contains information such as data record type (e.g. ASCII, signed float), formula and its coefficients used for value calculation, units, etc.

SecurityAccess

SecurityAccess service allows the client to unlock functions/services with restricted access.

CommunicationControl

CommunicationControl service allows the client to switch on/off the transmission and/or the reception of certain messages on a server(s).

Authentication

Authentication service provides a means for the client to prove its identity, allowing it to access data and/or diagnostic services, which have restricted access for, for example security, emissions, or safety reasons.

ReadDataByPeriodicIdentifier

ReadDataByPeriodicIdentifier service allows the client to request the periodic transmission of data record values from the server identified by one or more periodicDataIdentifiers.

DynamicallyDefineDataIdentifier

DynamicallyDefineDataIdentifier service allows the client to dynamically define in a server a DataIdentifier (DID) that can be read via the ReadDataByIdentifier service at a later time.

WriteDataByIdentifier

WriteDataByIdentifier service allows the client to write information into the server at an internal location specified by the provided DataIdentifier (DID).

InputOutputControlByIdentifier

InputOutputControlByIdentifier service allows the client to substitute a value for an input signal, internal server function and/or force control to a value for an output (actuator) of an electronic system.

RoutineControl

RoutineControl service allows the client to execute a defined sequence of steps to obtain any relevant result. There is a lot of flexibility with this service, but typical usage may include functionality such as erasing memory, resetting or learning adaptive data, running a self-test, overriding the normal server control strategy.

RequestDownload

RequestDownload service allows the client to initiate a data transfer from the client to the server (download).

RequestUpload

RequestUpload service allows the client to initiate a data transfer from the server to the client (upload).

TransferData

TransferData service is used by the client to transfer data either from the client to the server (download) or from the server to the client (upload).

RequestTransferExit

RequestTransferExit service is used by the client to terminate a data transfer between the client and server.

RequestFileTransfer

RequestFileTransfer service allows the client to initiate a file data transfer either from the server to the client (download) or from the server to the client (upload).

WriteMemoryByAddress

WriteMemoryByAddress service allows the client to write information into server’s memory data under provided memory address.

TesterPresent

TesterPresent service is used by the client to indicate to a server(s) that the client is still connected to a vehicle and certain diagnostic services and/or communication that have been previously activated are to remain active.

SecuredDataTransmission

SecuredDataTransmission service is applicable if a client intends to use diagnostic services defined in this document in a secured mode. It may also be used to transmit external data, which conform to some other application protocol, in a secured mode between a client and a server. A secured mode in this context means that the data transmitted is protected by cryptographic methods.

ControlDTCSetting

ControlDTCSetting service allows the client to stop or resume the updating of DTC status bits in the server(s) memory.

ResponseOnEvent

ResponseOnEvent service allows the client to request from the server to start or stop transmission of responses on a specified event.

LinkControl

LinkControl service allows the client to control the communication between the client and the server(s) to gain bus bandwidth for diagnostic purposes (e.g. programming).