We thoroughly rule them out by checking if the cabin wiring harness is melted, if the seat belts have water stains or mold, if there is unusual rust or debris in the seat tracks and cigarette lighter, and by verifying with the insurance company for any "total loss claims." These two types of cars are an absolute sales ban for us.

Once the car system (especially in a closed ecosystem) undergoes a major version upgrade, its bootloader is usually locked, preventing downgrades. If this happens, there is basically no solution in an overseas environment. Therefore, we strongly warn: do not blindly insert a USB drive to upgrade while offline.

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).