"Previously, when I went to the repair shop to read the fault code, they charged me 200 yuan. I couldn't stand it anymore and bought this myself. I never expected this little thing to be so powerful! When connected to the mobile app, it not only immediately read out the fault code P0420 (low efficiency of the catalytic converter), but also provided a Chinese explanation and maintenance suggestions. What surprised me the most was its real-time data stream function. While driving, I could see data such as engine load, oxygen sensor voltage, and short-term fuel correction, which helped me determine whether the oxygen sensor was broken or the three-way catalyst was blocked. It literally saved me a fortune in 'blind repair' costs. Combined with the included battery voltage monitoring function, I could check the generator status at any time. These few dollars were well worth it. I strongly recommend that old car owners keep one!"