Remote mechanical assessment relies on documented evidence: 1. Cold-start video: Ask for a video of the engine starting from cold — listen for rattles, watch for smoke (blue = oil burning, white = possible head gasket issue). 2. OBD scan: A full diagnostic scan reveals fault codes in the engine, gearbox, and electronics. Request the raw scan report, not a screenshot summary. 3. Service records: Cross-check mileage against maintenance records and inspection stickers; consistent records indicate a cared-for car. 4. Fluid check: Photos of the oil dipstick and coolant color tell a lot — milky oil or rusty coolant are red flags. 5. Test drive video: A short drive video shows gear shifts, braking, and steering behavior. Combine these with the pre-shipment inspection report. A seller who refuses to provide cold-start video or OBD data is a warning sign.

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.

It's extremely difficult. Unauthorized modifications can lead to module current overload protection, resulting in a lock. In China, you need to use the factory online engineer account to reprogram it. It's basically impossible to perform online decoding overseas. We strongly warn against blindly modifying the electrical systems of modern integrated circuit vehicles.