A 2012 mileage TOYOTA Camry car with a mileage of 5500km and a model of ACV51 L-JEPSKC. The owner reflected that the vehicle had been unable to start several times and required treatment. When the technician arrives at the scene, he starts the vehicle and starts the machine running, but it can not really start up. Fault diagnosis: the reasons that can be analyzed from the failure phenomenon to the fault may be: (1) the internal failure of the battery, the insufficient storage capacity, the short circuit of the battery plate or the oxidation and loss of the battery, resulting in loss of electricity from the discharge of the battery, that is, the loss of electricity caused by the internal discharge of the battery; (2) the insufficient power generation of the generator and the insufficient charge of the battery; 3. The power consumption of the electric appliance is large, which leads to the insufficient charge of the battery; (4) when the vehicles are not used, the useful electrical appliances are not closed because the electric devices, wire harnesses, sensors, controllers, actuators and other electronic components and circuits have caused leakage of electricity to make the battery lose electricity. This is called the battery external discharge, and this kind of leakage belongs to the battery. The latent circuit fault is the leakage fault that must be checked; 5. The dark current on the vehicle is too large to cause abnormal consumption. The battery must keep a trace of the external discharge current in the absence of the working state (that is, to pull the key and lock the car) to ensure the regular guard current of the security guard and so on. It is called the "dark current". This part of the dark current discharge is actually an external discharge in the normal category. The relative data of the battery are checked as follows: the density of the electrolyte is about 1.12 (the standard concentration of the battery is 1.28), the open circuit voltage is 10.05V (standard value is 12.5 ~ 13.8 V), the starting voltage is 6.37V (the standard value is above 9.6V), the voltage of the generator is 13.49V when the generator is no load, and the generator load voltage is 12.13V. The technician can get the replenish charge from the above data to be 11h. After charging is completed, the battery is installed on the vehicle to carry out the measurement, and the data is normal. On the second day, the data were again measured and returned to the state of failure. After communicating with the owner, the owner claimed that he had installed non factory quality navigation in other maintenance factories. The technician measured the dark current (the leakage current) and found that the current fluctuated from 16 to 75mA (standard value of 20 to 8mA), connected to the test lamp, and found that the test lamp flickered at a certain frequency, and the leakage current of the 75mA was certainly larger. So the technician found a model of the same model 2.0S, measured the leakage current of 23mA, but there is no current fluctuation phenomenon, which indicates that the leakage current of the fault car is seriously exceeding the standard. During the inspection, the technician found a relay working around the passenger chamber blower. The frequency of the relay was synchronized with the flicker frequency of the test lamp, looking for the relay as "light cut relay". Then the indoor light is opened, the ignition switch is closed, and after waiting for 20min, the indoor light is extinguished automatically, indicating that the relay coil has always been in the state of electricity, but it will not leak. The technician checks the power distribution box, when the 20A fuse RADIO-B is pulled out, the test lamp is darkened, the flicker disappears, the light cut relay will no longer appear repeatedly sucking, indicating that the fault is in the sound system.