What are the causes of the parking brake failure in the BMW 5 Series?
2 Answers
The causes of the parking brake failure in the BMW 5 Series are as follows: 1. Insufficient brake oil pressure: lack of oil in the brake master cylinder, brake pipeline rupture, oil pipe joint leakage, or oil circuit blockage. 2. Air in the brake system. 3. Excessive free travel of the brake pedal or excessive brake clearance: poor contact of the brake shoe friction plate, severe wear, or oil contamination. Relevant information about the automatic parking system is as follows: 1. Introduction: Automatic parking, also known as AUTO-HOLD, refers to an automatic braking function. After activating this function, for example, when stopping at a traffic light, there is no need to pull the handbrake, which simplifies the operation by avoiding the use of the handbrake or electronic handbrake. For automatic transmission models, frequent shifting from D to N or D to P is also unnecessary. 2. Working principle: The AUTO-HOLD automatic parking function provides accurate parking force through the slope sensor by the controller. During startup, the parking control unit calculates information provided by the clutch distance sensor, clutch engagement speed sensor, and throttle pedal sensor. When the driving force exceeds the driving resistance, the parking brake is automatically released, allowing the car to start smoothly.
I've repaired numerous electronic parking brake failures in BMW 5 Series, and found the main causes typically fall into several categories. First is the parking brake motor issue - BMW uses electronic modules to control the rear caliper motors, which can seize up or fail when water enters after prolonged use. Second are sensor failures, where the system can't detect brake pad position and throws an error. Excessive brake pad wear is another common cause - the parking brake will refuse to operate when thickness drops below 4mm. Wiring problems also occur frequently, particularly with corrosion at the wiring harness connector on the left side of the trunk. Failed software updates can additionally cause control logic confusion - some owners experienced sudden parking brake failure after battery replacement. Improper use is another factor, like failing to dry the motor after water exposure leading to rust. I recommend immediate inspection when the warning light appears, and advise against forcibly engaging the parking brake to prevent module damage.
