DTC Fault Code Detailed Explanation: C05B001

Fault Depth Definition

C05B001 (Brake Hydraulic L1 Circuit Leak) is a specific fault diagnosis code defined in the safety monitoring logic of the intelligent power braking system. In the vehicle braking control system architecture, triggering this fault code means that the control unit has detected unexpected fluid pressure attenuation or anomaly in the Brake Hydraulic L1 Circuit.

The core of this fault code lies in the closed-loop control verification of system pressure. As the system's core logic calculation hub, the Intelligent Power Braking Controller (Intelligent Power Braking Controller) continuously monitors the dynamic state of hydraulic circuits in real-time. When the system determines that the physical integrity of the circuit is compromised, causing uncontrolled loss of liquid medium under static or dynamic conditions, the system will output this code. This is not only a direct reflection of hardware leakage but also an important indicator of pressure feedback mechanism failure in control strategies, aiming to prevent vehicle dynamics control risks caused by insufficient braking pressure.

Common Fault Symptoms

When the C05B001 fault code is established and recorded in the onboard diagnostics system, car owners or repair technicians may observe the following specific system behaviors and driving experience changes:

• Intelligent Power Braking System Partial Function Failure: Vehicle active safety assistance functions (such as automatic emergency braking or kinetic energy recovery coordinated braking) may be restricted or completely disabled.
• Instrument Cluster Warning Indication: The brake warning light or electronic stability program indicator light on the dashboard may light up, prompting the driver that there is potential risk in the braking system.
• Reduced Braking Performance: Due to hydraulic circuit leakage causing pressure unable to be maintained at set levels, braking torque response lag or soft pedal feel when stepping on the pedal may occur.
• Fault Storage Status: This fault code will be written into the control unit's non-volatile memory for subsequent data reading and historical fault analysis.

Core Fault Cause Analysis

According to system architecture logic and fault performance, the triggers leading to the triggering of C05B001 can be categorized into the following three dimensions:

• Hardware Component Failure: Internal pressure sensors in the Intelligent Power Braking Controller suffer physical damage or electrical characteristic drift, causing their output signals to be unable to accurately map the true hydraulic state.
• Line/Pipe Medium Issues: Physical leak points appear in brake pipes (such as damaged sealing rings, pipe body cracks), causing loss of brake fluid; or air mixes into brake pipes, compressing the hydraulic transmission medium, causing abnormal pressure value fluctuations.
• Controller Logic Calculation Deviation: Although an extension of hardware component failure, a deviation in the internal pressure comparison algorithm of the Intelligent Power Braking Controller may misjudge normal physical fluctuations as leak events (i.e., control unit sensor signal judgment logic anomaly).

Technical Monitoring and Trigger Logic

The system performs real-time dynamic monitoring of hydraulic circuits through high-precision pressure sensor arrays, its fault determination logic is as follows:

• Monitoring Target: Deviation amount between Intelligent Power Braking Controller Hydraulic Actual Pressure Value and Set Pressure.
• Determination Threshold Conditions: When the controller calculates the difference between the above two ($\Delta P$), if this deviation value exceeds the set range, the system will immediately lock this state as a fault. The "set range" here refers to the safe tolerance interval determined based on vehicle calibration strategies, used to distinguish normal operating condition fluctuations from substantial leaks.
• Trigger Fault Condition: The monitoring logic is only effectively activated during the system self-check cycle after the ignition switch is placed in ON and during dynamic driving. At this time, if the pressure feedback signal continues to be maintained in an abnormal area and does not recover with time attenuation, the controller will determine fault establishment, turn on the dashboard alarm light, and execute partial function failure protection strategy to ensure driving safety.