Automotive diagnostic profile

I. Overview of Diagnosis

    Currently, OEMs and suppliers to adopt diagnostic methods online and offline diagnosing diagnosis combination.
Online diagnosis: it can in the car during the operation of the electronic control system of ongoing monitoring work of each component and, if abnormal, according to a specific algorithm determine the specific fault, and stored in code down, and start the corresponding module function trouble-free operation so faulty cars can be driven to a repair shop for repair, maintenance personnel can use the auto self-diagnostic function to call up the fault code, quickly locate and repair the fault. Therefore, the maintenance of safety and convenience standpoint, automotive electronic control system should be equipped with self-diagnostic function. Since 1979, General Motors pioneered the use of self-diagnostic function in its automotive electronic control systems, the major automobile manufacturers in the world to follow suit in the production of electric cars are each equipped with a self-diagnostic function. Self-diagnostics, and maintenance of new car factory has become an important means indispensable plant fault detection.
Offline diagnosis: read the corresponding diagnostic information through an external diagnostic equipment, and diagnostic operations. The key to diagnosis is how to achieve offline communication mechanism and diagnostic equipment and diagnostic services between the ECU, namely diagnostic protocol.


        Currently, the diagnostic protocol standard is divided into two systems, ISO (International Standards Organization) and SAE (Society of Automotive Engineers). United States to use SAE standard system, most countries outside the United States (including China) the use of ISO standards.

    In the passenger area, OEM positive diagnosis from a custom protocol, turning to ISO standards. In the field of commercial vehicles, OEM follow SAE diagnosis, on this basis, the European OEM increased ISO diagnosis. Table 1 lists some of the ISO and SAE standard control.



II. Related diagnostic criteria

Diagnostic criteria: a description of a series of diagnostic services, diagnostic request definition ECU and between the response rule, ECU for processing action request message and a request response packet information meaning.

1.ISO 14230

Keyword Protocol 2000 (KWP2000), is based on the K-Line (serial transmission, the maximum transmission rate of 10.4K) of diagnostic protocols, 14230 is a set of communications protocols have defined from the physical layer, data link layer to the application layer.

2.ISO 14229-1

UDS = Unified Diagnostic Services, defines only diagnostic services, and implementation of the network does not involve only the application layer.

3.ISO 15765

Diagnostic On CAN, CAN (serial transmission, the maximum communication speed 1M), defines the network transport layer (Part2).

Three .OBD-On-Board Diagnostics

OBD is a complex self-diagnostic system for detecting faults affect vehicle emissions components and systems.

All OBDII or EOBD equipped cars must have:
- Standardized data Diagnostic Interface (SAE-J1962),
- Standardization decoder (SAE-J1978)
- Standardized electronic communications protocol (KW2000, CAN, CLASSII, ISO9141, etc.),
- Standardized diagnostic trouble codes (DTC, SAE-J2012),
- Standardized intelligence service (SAE-J2000).

Four functional units .ISO 14229-1

1. Diagnosis and management of the communication function unit

DiagnosticSessionControl for session state to switch to access those services in a non-default session to access the
ECUReset for ECU reset, for example, after the ECU reprogramming, this service is required to reset ECU
SecurityAccess for protection and security, privacy, or emission-related data
CommunicationControl service requested by the user to control its communications
TesterPresent for maintaining a non-default session state
AccessTimingParameter user to an active communication read / modify the time parameters
SecuredDataTransmission user data security in a data transfer execution external
ControlDTCSetting opening / closing DTC Records
Start a user request event mechanism ResponseOnEvent
Baud LinkControl user requests for communication control unit 2. The data transmission capabilities
ReadDataByIdentifier read ECU fault information storage space by DID (Data Identifier)
ReadMemoryByAddress user to read the current value of memory through Address
ReadScalingDataByIdentifier DID read by diagnosis-related conversion formula
ReadDataByPeriodicIdentifier for periodically reading data DID
DynamicallyDefineDataIdentifier for once read multiple DID data, combined with the need to use 0x22 Service
WriteDataByIdentifier by DID write data
WriteMemoryByAddress user writes value 3. Storage data transmission unit via Address
Diagnostic information is stored in the ECU ClearDiagnosticInformation to clear storage space, such as freeze frame data, extended data, etc.
4. ReadDTCInformation for reading fault information input and output control unit
InputOutputControlByIdentifier user requests the control input / output5. Remote Activation function unit
RoutineControl routine control for start / stop routine within the ECU, or read its return value 6. upload and download function unit
RequestDownload user requests to download data
RequestUpload user requests to upload data
TransferData service user to transfer data (download) or request data from the server (upload)
RequestTransferExit user requests termination of data transmission

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