The warning device of the brake system is activated when driving. What does this mean?

The activation of the warning device for the brake system indicates a serious issue that affects the braking performance of the vehicle.

1. "Reserve pressure is no longer adequate" means that the pressure within the braking system has dropped below the safe operating level, which jeopardizes the effectiveness of the brakes.
2. "The brake system is probably defective" suggests that the overall integrity of the braking system is compromised, which could be due to various reasons, including wear and tear or mechanical failure.

Both of these points are critical as they signal that the vehicle may no longer be safe to operate.

The option regarding a leaking brake cylinder, while related, was not part of the selected answers but would also indicate a potential fault in the brake system, further emphasizing the need to address any warnings immediately based on German traffic regulations. Prompt investigation and repair of brake system issues are vital for vehicle safety and adherence to legal requirements.