Why is there a sound when stepping on the brake in P gear?

[DakotaLee]

It is normal to hear a sound when stepping on the brake in P gear. This is because the gear lock switch, which is installed on the brake pedal, is designed to prevent accidental gear shifting that could lead to traffic accidents. The lock is released only when the brake is pressed, allowing gear shifting. The sound is produced by the electromagnetic switch engaging when the brake is pressed. Here are some relevant details: 1. Shifting from P gear to any other gear requires pressing the brake, as this is a safety feature to ensure driving safety. Without pressing the brake, shifting from P to R or D could immediately generate backward or forward driving force, and the handbrake alone might not be sufficient to stabilize the car, potentially causing danger. Additionally, accidentally pressing the accelerator while not pressing the brake could lead to accidents involving people or property. Manufacturers now design unlock buttons that prevent shifting from P gear to other gears without pressing the brake. 2. Not all automatic gear shifts require pressing the brake. Only shifting from P gear to other gears mandates pressing the brake (shifting to reverse gear also requires pressing the brake first). Not pressing the brake could damage the parking gear, but switching between other gears does not require pressing the brake.

[Lucian]

This issue needs to be analyzed in three parts: First, identify the sound source. The crisp 'click' sound from the transmission area is normal ratchet unlocking. The squeaking sound under the brake pedal requires checking the vacuum booster pump's seal. If you hear a metal scraping sound from the chassis, it might be due to rusted brake pads not fully separating. Here's a practical self-check method: When the car is cold, splash some water from a water bottle onto the brake discs and then press the brakes. If it produces a brief sharp sound, it indicates a brake pad issue. During my last maintenance, the technician demonstrated this and explained it's caused by excessive metal content in the brake pads, but it doesn't affect safety.