Any brothers know why the car beeps for a few seconds when you turn on the power, but doesn't show any issues or faults?

The second key hasn't been used for a while. Recently, I took it out and found that the remote doesn't work. I changed the battery, but it still doesn't work. Does anyone know why?

Why does the transmission often show a fault code and then disappear on its own shortly after?

Why does the car show a transmission fault warning during a cold start, but it goes away after waiting and restarting?

Even with power in the battery, my Jinxuan manual sometimes doesn't respond when starting. After turning it on and off a few times, it starts. Does anyone know what might be causing this?

Why doesn't my fuel consumption display anymore? It's always showing "——————".

Does anyone know why there's a high-pitched buzzing sound inside the car as soon as it's powered on? It's been happening the last few days and it's giving me a headache.

Any brothers know why the car beeps for a few seconds when you turn on the power, but doesn't show any issues or faults?

Does anyone know about the Haval H2? Initially, when you pressed once, it would turn off, and pressing a second time would cut off all power in the car. Now, pressing once turns it off, and pressing a second time puts it in a powered self-check mode. Does anyone know what might be the problem? Has any owner experienced the same issue? Thanks!

Is it a problem with the ignition switch if the Volvo S40 key is turned to the second position, but there's no power and it reports an engine anti-theft system fault? I changed the ignition switch, and now it's sometimes good and sometimes bad. Sometimes the dashboard lights up, sometimes it doesn't, and sometimes it even starts automatically.

The compass on the dashboard is always showing north and doesn't move. Does anyone know how to adjust it?