This indicator lamp lights up. What could be the cause of this?

This indicator lamp is related to the tire pressure monitoring system (TPMS). It lights up when there is an issue with the tire pressure of one or more tires.

The light can come on for two main reasons according to German traffic rules:

1. The inflation pressure is too low in one tire. This means the tire might be underinflated, which can reduce driving safety, cause uneven tire wear, and increase fuel consumption.

2. A recently performed wheel change. After changing wheels, the system may need time to reset or recalibrate, which can cause the warning light to come on temporarily.

A loose wheel nut is not indicated by this lamp. If a nut is loose, you would typically have other indicators or symptoms like unusual vibrations or noises.

Understanding this lamp ensures you regularly check tire pressure and after services like wheel changes, so your vehicle remains safe and efficient.