What are the methods of automatic transmission fault diagnosis?

The routine inspection of automatic transmission mainly refers to the analysis of fault causes according to the surface phenomena of automatic transmission reflected by users through seeing, hearing, touching and smelling. Routine inspection is an essential step in the process of automobile automatic transmission maintenance, and it is the basic inspection before the professional test of automatic transmission. If these routine inspections are not carried out, the subsequent tests may directly cause more damage to the transmission.

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(1) There are many models and manufacturers of automatic transmissions. There may be several different combinations of the same engine and transmission, and the performance and structural parameters of different combinations of transmissions may be different. So first of all, you should know the vehicle model, production year, automatic transmission model and other information after contacting the vehicle, which is conducive to the later fault diagnosis. The identification of the transmission can be confirmed by the nameplate, as shown in Figure 5- 1.

(2) Appearance inspection: Look at the external conditions of the automatic transmission when parking. Check whether the automatic transmission leaks oil, the oil pan is deformed, the rubber sleeve of the transmission suspension is damaged, the output shaft of the automatic transmission is loose and disconnected, the wiring harness of the automatic transmission is broken (scratched), the connector is loose, the grounding between the automatic transmission and the vehicle body is firm, the oil pipe of the automatic transmission passing through the radiator is bent or squeezed, the radiator of the water tank is dirty, and the shift handle is bent and deformed. In the vehicle, check whether the throttle cable or pull rod of the automatic transmission is too loose or too tight (full hydraulic automatic transmission), whether the adjusting screw of the throttle position sensor is loose (electronic automatic transmission) and whether the wire connector is firmly inserted. These inspections must be careful, because many faults are late and difficult to upgrade, which are caused by these simple reasons. When checking the throttle cable, turn the throttle by hand while watching to see if the throttle cable can return to its original position. Sometimes there is burr or fracture in the middle of the cable, which will affect the return of the throttle valve, thus affecting the upshift and downshift of the automatic transmission.

(3) Listening is to make full use of people's ears to judge the position of abnormal sound, identify the fault of transmission or engine, and analyze the possible reasons. In this process, we can make full use of some tools and equipment, such as long screwdriver, special stethoscope, endoscope and other instruments and tools to make the diagnosis more accurate.