oliverberger10

Mercedes GT Roadster High Voltage Error

I'm starting to lose my mind here. I've got a 2021 Mercedes GT Roadster, hybrid engine, with about 96000 km on it. Recently, I keep getting this annoying "High-voltage system error" message popping up. It's stored in the error memory, which I can read out. What's worse, sometimes the engine just decides to shut off completely, and I get seriously reduced engine power at other times. I suspect it's a battery issue, like maybe it's heavily discharged or even defective. I did a quick check of the electrical wiring and didn't see anything obvious, no cable damage that I could spot. Could a battery drain cause all this? I am not an expert, but I have some knowledge about cars. Any ideas before I take it in and get robbed?

4 comment(s)

Sounds familiar. I had a similar problem with my old BMW i3, although it wasn't quite as dramatic. I also got high-voltage system warnings. Is your 12V battery OK? In my case, the small 12V battery was causing all sorts of weird issues with the main high-voltage system. Think of it like a small cog jamming up a big machine.

Interesting! I hadn't really considered the 12V battery. I mean, I assumed it was fine since everything else seems to be working – lights, radio, etc. But if that was the culprit, wouldn't that be something? How did you figure out it was the 12V battery and not something more serious with the main high-voltage system? Did you also have an electrical fault stored?

Well, the i3 is known for that issue. I was getting odd electrical faults and weird behavior. Eventually, the car wouldn't start. A simple battery test showed the 12V was toast. Given your symptoms, it's worth checking. But honestly, with a high-voltage system error, it's probably best to get it properly diagnosed by a workshop. It could be something simple, but it could also be a more serious issue with the hybrid system itself. Don't risk it.

You were spot on. Turns out the 12V battery was indeed the problem. I got it tested, and it failed miserably. Replaced it, and the high-voltage error is gone, engine runs perfectly, and no more power reduction. The whole thing cost me 290€, including the battery and installation. Thanks a bunch for pointing me in the right direction! Saved me a ton of stress and probably a fortune compared to having the main battery replaced.

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