The catalytic converter contains precious metals, making it a target for theft. During chassis inspection, we check if the welding points of the catalytic converter are in their original state. Once verified, the vehicle will be sealed after being handed over to port logistics to prevent disassembly and resale.

We use two steps: 1. Insert a medical-grade endoscope through the spark plug hole to visually inspect cylinder wall scratches and carbon buildup on the piston top; 2. Extract an engine oil sample to check for large metal debris or emulsification (caused by coolant leakage).

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.