In 11/2024, I started experiencing intermittent noises coming from the engine compartment of my 2011 Toyota Prius. The initial sound resembled the buzzing noise generated when first starting the vehicle. Then the noise started to persist for extended periods after the vehicle was turned off. It would oscillate between buzzing for approximately 10 seconds & remaining dormant for about 1 minute, repeating this cycle. The duration of these cycles could extend for up to 20 minutes. Concurrently, I experienced several instances where the brake pedal would abruptly become stiff & difficult to press. Notably, no warning lights were illuminated on the dashboard. Recognizing these symptoms as unusual, I conducted online research and discovered that the issue could potentially stem from a malfunction in the brake booster pump and assembly. Given the potential for a loss of braking power and the risk of personal/public safety, I scheduled a diagnostic inspection at Toyota of Poway, Poway, CA, on 12/18/2024. It confirmed the presence of a problem with the brake booster pump and associated components. In light of this diagnosis, I made the decision to refrain from driving the vehicle until the repairs were completed. The repair costs amounted to $3,475.47. I found I had received a notification from Toyotas Customer Support Program, designated as Customer Support Program Notification-ZJB. This notification explicitly acknowledged this defect & provided a repair coverage policy that stipulated a coverage policy of which Im no longer entitled to. Despite not meeting the eligibility criteria for the repair coverage program, I am deeply troubled by the fact that this recognized defect persists in vehicles currently on the road, such as mine, without any corresponding recall action and subsequent repair costs covered by Toyota. Fortunately, I was spared from any accidents as a direct consequence of this issue. Many similar complaints here support this dangerous issue!