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Through establishing the communication between automotive diagnostic scanner and automobile computer, get shared data out from RAM of the vehicle computer ECU to analyze vehicle trouble, so the data stream testing function is an important function of auto engine obd code reader . Data stream is divided into static data (KOEO) and dynamic data (KOER). All vehicles that adopting ECU fault self-diagnosis system can use vehicle diagnostic code reader to readout the the data stream that output by various vehicle electronic control unit ECU through diagnostic socket and reflecting the electronic control unit controls system working conditions. Maintenance personnel can judge whether the electronic control devices work properly by making numerical analysis of various parameters of data stream, providing the basis for finding cause of the malfunction.
Parameters in data stream has two forms, the numerical parameter and status parameter. The numerical parameter is the parameter that has certain units and a certain change range, which usually reflects the operating voltage, pressure, temperature, time, speed, etc. of each part in the work of the electronic control unit; state parameter is those who have only two state, such as on or off, closed or disconnected, high or low, yes or no, etc., it usually signify the working condition of the components of electronic control devices such as switches and solenoid valve.
In conducting numerical analysis, you must first distinguish between the various parameters are input signal transmitted to ECU from the sensor of electronic control device or the output command sent to the electronic control unit actuator by ECU. Input signal parameters can be state parameters, so can be numeric parameters. Most of the output command parameters are state parameters, a small part is numerical parameters. Data stream parameters can be classified according to various systems of vehicle and engine. Parameters of parameters of different types or different system have different analysis methods. During electronic control unit failure diagnosis parameters of several different types or different systems are needed to go through comprehensive contrast analysis. Different brands and different models of vehicles, the name and content of electronic control device data stream parameters are not exactly the same.
The various parameters of currently common Automotive electronic control unit data stream are classified according to different systems and types, and explain its meaning, form of parameters and the unit of numerical parameters and change range. As ECU of different models determined the content of their own data parameters, therefore, when detects certain vehicle model, only part of all of the following parameters will show up on the automotive scan tools .
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