Which of the following would signal a failure during a parking brake inspection?

During a parking brake inspection, one critical aspect to evaluate is whether the parking brake effectively holds the vehicle in place when fully engaged. If the parking brake does not keep the vehicle stationary on an incline, this indicates a failure in its operation. The primary function of the parking brake is to secure the vehicle, preventing it from rolling away when parked. Therefore, if it fails to hold the vehicle when fully applied, it represents a significant safety concern and signals that maintenance or repairs are necessary.

Other options, while relevant to the functioning of the parking brake, do not indicate a failure. For example, a parking brake that engages smoothly without noise demonstrates that it is functioning properly. Additionally, if the parking brake acts as a secondary brake, this can be viewed positively, as it indicates the system can provide additional stopping power if needed. Lastly, if the parking brake releases automatically when shifted to drive, it can be a designed feature of modern vehicles to enhance convenience, not a sign of a failure. Each of these aspects highlights proper functions rather than issues, making them irrelevant in identifying a failure during the inspection.