4S dealership records are directly connected to the manufacturer's database, making the data hard to tamper with and the most reliable, with original parts guaranteed; third-party repair shops usually are not connected, making their data unverifiable. Therefore, we only consider the connected records from 4S dealerships as valid historical documentation.

We will directly check the registration certificate (the big green book) and count the number of changes.

The technician will put the vehicle in neutral on the lift, rotate the wheels, and listen for any abnormal metal gear whine from inside the motor reducer, and check for gear oil leaks at the joints of the reducer housing.