Fault Code Setting Conditions-diagnose by Fcar auto diagnostics tools

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Fcar auto diagnostic tool can diagnose systems such as: Engine, ABS, Transmission, Airbag, Body Electronic equipment, Smart Key System, Anti-theft System, Power Steering, Cruise System, Instrument System, Gateway, Air-Conditioning System, Sound System, Light System...
The whole control system of a vehicle is composed of many subsystems (sensors, actuator elements, power supply, controller) circuit composed. Therefore, the content of trouble code contains not only the sensor or actuator elements failures, but rather showing that the signal of the system is abnormal , which may be caused by any part of the (components, connectors, circuit, or computer), so fault code read out by car diagnostics tool only provide the general direction of further testing for maintenance personnel, but does not tell us exactly what and where occurred failure. Therefore, fault codes mainly play the role of the maintenance guidelines.

When engine is working normally, Trouble self-diagnosis system will monitor the components of Electronic control system and ECU own work, the LEV between the signal to ECU from the sensors and the control signal from ECU both are in the normal range. Once the input or output signal of ECU is not in the normal range, self-diagnosis system will point out the trouble about the signal, meanwhile the light on the dashboard will be immediately lit and store relevant trouble code into ECU’s memory. When starting the diagnostic operation, you can get out the trouble code through auto diagnostic equipment, which brings great convenience for the clearance of fault codes. However, if used incorrectly or rely on the trouble code too much, blindly repair or replace some components without any analysis. It can’t solve the problem and even it will result in new trouble and more problem.

The significance of checking diagnostic trouble code setting conditions carefully is that: as vehicle maintenance personnel, he must know when did the vehicle's fault happen? Fault code is triggered because of what conditions? How to simulate conditions that the fault occurred?

Fault codes display in vehicle diagnostics tool tells you a certain system of the vehicle occurred a certain failure at present or in the past. Therefore only after being repaired, the fault code no longer appears and this shows fault information have been cleared. But remember, fault code may disappear because of inexistence of the fault. Similarly, if the fault monitoring system program was suspended because of the restriction of certain conditions, fault code will not appear either.