Principle of automobile fault diagnosis?

Four basic principles of automobile fault diagnosis;

(a) the principle of simplicity before complexity, easy before difficulty.

(2), think twice before you act, the principle of cooked before cooked.

(3) The principle of going up first and then down, and going outside first and then inside.

(4) The principle of first use and code priority.

(1) Look before you leap.

Firstly, the fault phenomenon of electronically controlled gasoline injection engine is analyzed comprehensively, and then the fault is checked on the basis of a preliminary understanding of the fault causes to avoid the blindness of fault diagnosis.

(2) first outside and then inside.

When the engine fails, first check the suspected faulty parts outside the electronic control system. In this way, unnecessary inspection can be avoided. For example, it was originally a fault unrelated to the electronic control system, but first, the components, devices and circuits of the electronic control system were inspected in a complicated way, but the real fault position was not found.

(3) Simple before complex.

Priority should be given to those suspected faulty components that can be checked by simple methods. We can use people's senses, such as asking, looking, touching, listening and trying, to quickly find out some obvious fault parts.

(4) Easy first, then difficult.

Engine failures are usually caused by some assemblies or parts. Those parts with common faults should be inspected first, and then other parts with unusual faults should be inspected. This can not only quickly troubleshoot, but also save time and effort.

(5) Code takes precedence.

When the electronically controlled gasoline injection engine fails, the engine failure warning light will flash to remind the driver. But for some faults, the self-diagnosis system only stores the fault code and does not give an alarm. Therefore, before the engine is checked by the system, the fault code should be read according to the method provided by the manufacturer, and then the fault should be eliminated according to the content of the fault code.

6. Accumulate data.

Accumulating data means that maintenance data related to the model should be prepared before maintaining the model. Besides collecting and sorting out these maintenance data from maintenance manuals and professional books and periodicals, another effective method is to detect and record the relevant parameters of trouble-free vehicles at any time.

In this way, through gradual accumulation, these test parameters accumulated at ordinary times can be compared with the measured parameters when repairing the same type of vehicles in the future, for the reference of maintenance personnel.