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 use a megohmmeter (insulation resistance tester) to measure the insulation resistance of the high-voltage bus. If the resistance value is below the national safety standard, it indicates a risk of leakage, and the vehicle will be deemed unqualified.

Interior assessment is divided into three core areas: the driver's high-frequency contact area (steering wheel, gear shift, edge of the driver's seat), central control button area, and rear seats and ceiling. The natural sheen of leather surfaces (patina) is normal; however, any physical damage (such as leather tearing, fabric burn holes, or plastic breakage) will be classified as "structural interior damage" and clearly marked.