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).

There are various reasons, including but not limited to: financial needs, restrictions from lottery policies, moving abroad, or dissatisfaction with certain features of the vehicle. We will ensure that the vehicle was not sold due to catastrophic failures by ruling out major accidents, water damage, and flooding.