Mercedes G63 Owners: That ‘Auxiliary Battery Low’ Warning Isn’t What You Think

” The first question many drivers ask is whether the vehicle actually has a separate auxiliary battery. The answer is yes—it does, and it’s located beneath the glove box on the passenger side. It’s a small, rectangular unit that powers secondary systems like the stop-start function, interior lighting, and some convenience features.

The bigger question, however, is whether replacing that battery requires a trip to the dealer for a software coding procedure. The owner reported that their dealer insisted the new battery must be “coded into the ECU” after installation. While BMWs often require battery registration to reset the charging system, Mercedes-Benz vehicles—including the G63—do not universally demand coding for the auxiliary battery.

Many independent Mercedes specialists and experienced DIY owners have swapped this battery without any coding step, and the system simply adapts.

That said, there is a nuance. If the main battery is replaced on a Mercedes, registration is typically recommended to tell the alternator the battery’s age and type. But for the auxiliary unit, the coding claim from the dealer may be an upsell or a misunderstanding. The best course of action is to replace the battery yourself or with a trusted independent shop, clear any warning lights with a basic OBD scanner, and see if the issue resolves.

If the warning persists, it could indicate a deeper charging system problem. For most G63 owners, a simple swap without coding will do the trick.