The most common reason for a malfunctioning Eco Start Stop system is a low battery charge. This could be either the main starter battery or the auxiliary battery (sometimes a capacitor). A long drive should sufficiently recharge the batteries. Even with some overnight drain, the battery should recharge while driving.
If you have a trickle charger, try fully charging the main battery to see if that resolves the issue. If not, one or both batteries might need replacing. A professional diagnostic tool (like STAR) or a battery load test at an auto electrician’s can pinpoint the faulty battery. The system may also reveal unrelated faults affecting the Start/Stop function. If it’s unclear which battery is at fault, consider replacing the auxiliary battery first. If the problem persists, replace the main battery as well.
Alternatively, you could continue driving without the Start/Stop function. Even if the battery isn’t optimal for this feature, it might still provide reliable service for months or even years. Many drivers choose to disable the system anyway.
