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).

The technician will start the vehicle and turn on the air conditioning system, measuring the actual temperature at the vents at the lowest and highest settings with a thermometer; at the same time, they will connect a manifold pressure gauge to check if the refrigerant pressure in the high and low pressure lines is within the normal range, determining if there is a chronic refrigerant leak.