Analysis steps of data flow analysis when there is fault code

There are two cases of fault diagnosis using data flow analysis: one is that the electronic control system stores fault codes; The other is no fault code. Let's take a look at the analysis steps when there is a fault code in data flow analysis.

In the process of troubleshooting the automobile electronic control system, by reading and confirming the fault code, when the fault code does exist, the general steps of data flow analysis are as follows:

First, check the frozen data frame when the fault code is recorded, and then confirm the running state of the vehicle when the fault code is generated, so that the vehicle can verify the fault under the condition indicated by the frozen data frame, and use the fault code to quickly and accurately determine the fault position.

When a fault code is confirmed, we can directly find out each group of data related to the fault code for analysis, analyze the causes of the fault code according to the conditions set by the fault code, then analyze the numerical waveform of the data, and finally find out the fault point.

Example:

A Dongfeng Citroen Elysee SX 1 car is equipped with AL4 automatic transmission. The "S" and "*" lights on the dashboard flash occasionally, and the automatic gear upshift is too late. Test the automatic transmission ECU with the special scanning tool PROXIA, read the fault code, and find the fault information listed in the following table.

According to the recorded fault code, first check the data flow of the throttle position sensor to determine the fault. When the ignition switch is in the M position, the engine is not started, and the accelerator pedal is completely released, the automatic transmission parameters are measured by PROXIA. It is found that the throttle opening parameter changes from 1 1.5 to 40.8. When the terminal of the throttle position sensor is pulled by hand, the throttle opening parameter is stable at 1 1.5. At the same time, the automatic transmission fault indicator light stops flashing, and when it is pulled again, the throttle opening parameter keeps changing again, and the automatic transmission fault indicator light flashes again.

Through the above dynamic data detection, it can be judged that the fault of the vehicle is the poor contact of the connector of the throttle position sensor. Because the ECU of automatic transmission can't get the accurate throttle position signal, it can't control the shift under normal circumstances, which leads to the shift delay. After replacing the throttle position sensor, troubleshoot the delayed shift.