A TOYOTA Milla car with a mileage of about 140 thousand km and a 2ZR-FE engine assembled 2008. Users reflect: 3 days without the car will start difficulties, mainly caused by battery loss. The failure phenomenon has appeared many times. Fault analysis: first of all, the battery test is used to detect the battery. It is found that the battery voltage is low. The test results show that the battery is good but needs to be charged. Then the battery is charged first, and then the battery is filled with 2H. The battery is good and the voltage is 12. 67V. Next, the parasitic current of the car is detected. The result shows that the parasitic current is 122. 6mA, which is obviously higher than the standard value of 30 ~ 50mA. Therefore, the phenomenon of excessive parasitic current in the electrical system of the car is shown. After communicating with the user, the car had installed the GPS-ONE anti-theft system. It suspected that the parasitic current caused by the electrical appliance was too large. Then the GPS-ONE anti-theft system was removed and the parasitic current was detected again. The parasitic current at this time was 6.61 mA left right, indicating that the parasitic current was very standard at this time. . Therefore, it can be judged that the excessive parasitic current is mainly caused by electrical equipment modification. Troubleshooting: removal of electrical equipment after installation, troubleshooting. Fault review: one of the important reasons for the loss of the battery after the installation of electrical appliances after the user is installed, is to avoid the occurrence of the failure, but can we consider the reduction or avoidance of excessive current on the basis of the dismantling of the GPS anti-theft system? I believe the answer is affirmative.