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).

Yes. We will use a professional diagnostic tool to scan all vehicle systems, including the Engine Control Unit (ECU), Transmission Control Module (TCM), Anti-lock Braking System (ABS), and Airbag Module (SRS), and provide English screenshots of all current and historical Diagnostic Trouble Codes (DTCs).

The headliner is considered an "irreversible interior component." If the edges are delaminated or there are deep, hard-to-clean dark water stains, it will directly lead to a downgrade in the interior grade, even if it does not affect driving. We will not use pins or low-quality glue for cosmetic repairs.