What are the reasons for parking brake failure?

[McBarrett]

Here are the reasons for parking brake failure: 1. Excessive clearance between friction pads and brake drum, oil contamination on friction pads or brake drum, severe wear of friction pads, exposed rivets, or surface hardening causing slippage. 2. Severe wear of parking brake pin shaft, excessive clearance, or over-adjusted parking brake lever. Additional information: 1. The parking function refers to when the engine is running or the vehicle is in motion, the parking brake is implemented through the DSC hydraulic system acting on the front and rear axle disc brakes. 2. When the engine is off and the vehicle is stationary, the parking brake operates via an electromechanical servo unit that manipulates the cables acting on the dual self-energizing drum brakes on the rear axle.