V40 Auxiliary Battery Error

I'm having a strange issue with my 2017 Volvo V40 diesel. It's done 204394 km. I'm getting an error message in the speedometer related to the auxiliary battery. I've also checked the error memory and there's a corresponding fault code. When starting, the engine feels weak, like the battery is struggling, and I've noticed some general electrical malfunctions, like the interior lights flickering slightly. I suspect the auxiliary battery isn't charging properly. Has anyone experienced something similar? I'm trying to gauge if it's a simple fix or something more complex before I take it to a shop.

4 comment(s)

Sounds familiar. Had a similar gremlin with my BMW 3 series. Auxiliary battery kept throwing errors. Symptoms were like a weak circulatory system in a human body. Have you checked the voltage across the battery terminals when the engine is running? Could be a faulty alternator not topping it up.

Thanks for the quick reply! I haven't checked the voltage while the engine is running, but I did check it when the car was off, and it seemed a bit low. What was the eventual cause in your case with the BMW?

Turned out to be a dead auxiliary battery. Voltage drop was causing all sorts of weirdness. If your voltage is low even when off, it's probably toast. Best bet is to get it tested properly at a workshop. Save yourself the headache.

Thanks for the advice! I took it to a local shop, and you were spot on. The auxiliary battery was indeed the culprit. They replaced it for 290€, and all the errors are gone. Starts like a charm now. Appreciate the help!

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